Juwitha Rawung

Berkat Sahabat

juwitharawung — Thu, 13 Mar 2008 07:21:02 +0000

Berkat Sahabat
Oleh: Tidak Diketahui
Ini kisah persahabatan dua anak manusia. Yang seorang adalah putra presiden, yang lain pemuda rakyat jelata bernama Pono.

Persahabatan ini sudah terjalin sejak mereka masih di bangku sekolah. Pono punya kebiasaan yang kadang menjengkelkan. Apa pun peristiwa yang terjadi di depannya selalu dianggap positif. “Itu Baik!” katanya senantiasa.

Hari itu seperti yang sering mereka lakukan, Pono menemani sahabatnya berburu. Tugasnya membawa senapan dan mengisi peluru agar selalu siap digunakan. Entah kenapa, barangkali belum terkunci secara sempurna, setelah diserahkan kepada sahabatnya senapan itu meletus. Akibatnya cukup fatal. Ibu jari putra presiden terkena terjangan peluru dan putus. Melihat itu tanpa sadar dengan kalemnya Pono berkomentar. “Itu Baik!” Kontan sahabatnya naik pitam. “Bagaimana Kau ini! Jempolku putus tertembak, malah dibilang Baik. Brengsek!” Agaknya, kali ini kelakuan Pono tak termaafkan. Ia dijebloskan ke penjara.

Beberapa bulan kemudian, sang putra presiden kembali pergi berburu ke Afrika. Malang, ia tersesat di hutan lebat dan ditangkap suku primitif yang masih kanibal. Malam harinya, dalam keadaan terikat ia akan dibakar untuk disantap ramai-ramai. Anehnya, mendadak ia dibebaskan. Belakangan ketahuan, suku tersebut pantang memangsa makhluk yang organ tubuhnya tidak lengkap.

Nasib baik itu membuat sang putra presiden termenung. Ia teringat kembali peristiwa ketika jempolnya putus tertembak lantaran ulah Pono. Ia kemudian menemui Pono di penjara.

“Ternyata Kau benar. Ada baiknya jempolku tertembak,” katanya sambil menceritakan peristiwa yang baru saja dialaminya di Afrika. “Aku menyesal telah memenjarakanmu.”

“Oh, tidak!’ Bagiku, ini Baik!”

“Bagaimana kau ini? Memenjarakan teman kau bilang baik?”

“Kalau aku tidak dipenjara, pasti saat itu aku bersamamu.”

Kisah satir ini mengingatkan pada pernyataan Randolph Bourne, intelektual Amerika yang juga anak didik John Dewey. Katanya, seorang teman itu memang dipilih untuk kita berdasarkan hukum perasaan yang tersembunyi, bukan oleh kehendak sadar kita si manusia.

Tips Eratkan Persahabatan

juwitharawung — Thu, 13 Mar 2008 07:18:55 +0000

13 tips eratkan persahabatan 1. KESABARAN

Belajarlah bersabar sekiranya sikap teman baikmu itu menyinggung perasaanmu, mungkin dengan kesabaranmu, temanmu itu akan mulai berubah & mula berfikir tentang hati & perasaan orang lain.

2. BERTERUS TERANG

Jgn sesekali kamu memendam perasaan jika kamu tdk menyenangi sikap teman2 di sekelilingmu. Cuba berbincang & berterus terang agar masalah yg membelengu dirimu aka selesai & jgn meninggikan suara ketika berbincang.

3. IKHLAS

Sentiasa bersikap ikhlas & jgn terlalu berkira dgn org lain. Sikap ikhlas kita akan menjadikan teman disekeliling akan lebih menghormati kita.

4. SALING MENGHORMATI

Saling hormat menghormati. Hormatilah org disekelilingmu & sudah tentu org lain juga akan menghormatimu.

5. JUJUR

Belajarlah menjadi seorang yg jujur. Saling percaya mempercayai menjadi hubungan persahabatan yg dijalinkan akan berjaya. Sebaiknya, buang jauh2 sikap bermuka-muka kerana ianya sikap merenggangkan persahabatan.

6. SALING FAHAM MEMAHAMI

Saling faham memahami & tdk berprasangka buruk adalah resepi utama dlm membina sebuah persahabatan yg berjaya.

7. SALING MEMAAFKAN

Jadilah seorang yg pemaaf sekiranya teman baikmua menyinggung perasaanmu. & ketahuilah, sikap pemaaf itu merupakan satu perbuatan yg mulia. Malah dia dpt memberikan kesan positif terhadap diri kamu sendiri.

8. BERTOLAK ANSUR

Saling bertolak ansur juga merupakan satu faktor penting utk membina sebuah perhubungan yg murni. Sifat begini akan memberi manfaat pada diri kamu & orang lain. Namun usah mengharapkan hanya org lain yg perlu bertolak ansur dengan kamu & dlm masa yg sama kamu pula mengambil kesempatan ke atas mereka. Ini tdk adil namanya!

9. JAGA TUTUR KATA

Jagalah tutur kata & jgn terlalu celupar ketika berbicara bersama teman-teman sekeliling kamu. Sikap lepas kata begini akan mengundang perselisihan faham antara satu sama lain.

10. NASIHAT MENASIHATI

Saling tegur menegur & nasihat menasihati antara satu ama lain. Teguran hendaklah secara baik & bukannya dgn melulu & mengkritik. Bukankah saling ingat- mengingatkan itu satu perbuatan yg mulia?

11. AMBIL BERAT

Jgn pentingkan diri sendiri, sebaliknya ambil berat antara satu sama lain. Contohnya, jika temanmu sedang dilanda masalah. Berada di sisinya ketika dia sedang susah merupakan satu pengorbanan besar & tanda setia kawan. Ia memberikan kekuatan & sedikit bebanyak masalah yg ditanggunginya akan berkurangan. Tapi awas! Jgn nanti sampai kamu tak tahan telinga jika saban hari terpaksa mendengar luahan masalahnya. Kadangkala kamu juga punya masalah yg perlu diselasaikan!

12. SALING BERHUBUNG

Jauh dimata, dekat dihati. W/pun mungkin kamu dipisahkan oleh jarak & kesibukan, apa kata kamu eratkan persahabatan dgn bertanya khabar. Telefon @ sekadar menghantar sms pun dah mencukupi tanda ingatan kamu kepadanya.

13. BERTELINGKAH

Sesekali bertelingkah yg berlaku akan menjadikan perhubungan bertambah baik. Kita lebih sling mengenali & memahami antara satu sama lain. Tapi haruslah diingat, bergaduh tanpa bermaafan tak guna juga. Sekurang-kurangnya kita kenalah beralah, bermaaf-maafan agar kekeruhan yg melanda akan jernih semula.

Sahabat Allah

juwitharawung — Thu, 13 Mar 2008 07:13:53 +0000

Sahabat Allah

11 09 2007

Yak 2:20-24 “Hai manusia yang bebal, maukah engkau mengakui sekarang, bahwa iman tanpa perbuatan adalah iman yang kosong? Bukankah Abraham, bapa kita, dibenarkan karena perbuatan-perbuatannya, ketika ia mempersembahkan Ishak, anaknya, di atas mezbah? Kamu lihat, bahwa iman bekerjasama dengan perbuatan-perbuatan dan oleh perbuatan-perbuatan itu iman menjadi sempurna. Dengan jalan demikian genaplah nas yang mengatakan: “Lalu percayalah Abraham kepada Allah, maka Allah memperhitungkan hal itu kepadanya sebagai kebenaran.” Karena itu Abraham disebut: “Sahabat Allah.” Jadi kamu lihat, bahwa manusia dibenarkan karena perbuatan-perbuatannya dan bukan hanya karena iman“

kata pak pdt, bagi yg pernah baca dr kitab kejadian mpe wahyu ga ada seorgpun yg disebut sahabat Allah kecuali Abraham, so pasti kita2 sendiri sebagai anak Tuhan jg disebut sebagai sahabatNya ada koQ ayatnya tapih seperti biasa sayah lupa bwakakakakak *ketahuan malesnya* nahhhhhhh jadih berhubung status kita sama dengan Abraham dalam artian sama2 sahabat Allah, gimana sih biar kehidupan kita kek Abraham gto loh…. selalu dekat dengan Tuhan, diberkati Tuhan, deelel… berhubung ayat2 yg dibagiin ma pdtnya ~~ilang~~ g dah lupa huahua jdnya cm inget ada 3 poin la intinya
1. Selalu percaya ma Tuhan
kayak Abraham, dia selalu percaya ma Tuhan, wkt Tuhan blg istrinya Sarah akan mengandung di usia Sarah yg ke 90an ya? *loh kok malah balek nanya wekekek* si Abraham tanpa neko2 tanpa ngmg byk ke Tuhan, dia hanya percaya pada Tuhan, tus wkt Tuhan minta Abraham mempersembahkan anaknya Ishak, dia jg nurut aja tanpa neko2 tanpa negosiasi ma Tuhan dl, padahal dia bisa aja nego ma Tuhan kek wkt Tuhan mo musnahin kota Sodom. intinya harus percaya aja deh *maksa* :p

2. Selalu mengasihi Tuhan lebih dr apapun
nah klo ini dah jelas bgt deh Tuhan ingin kita mengasihi Dia lebih dr apapun jg jd Dia itu selalu diatas istri/suami/keluarga/karir. pokoknya Tuhan selalu yg d first deh… huehue kisah Abraham mana yg pdt itu bahas? lagi2 ~~ngilang~~ lupa hehehe *jemaat teladan* :p

3. Mengasihi yatim piatu & janda2 (manusia)
nah yg ini nih g inget :p Yak 1:27 Ibadah yang murni dan yang tak bercacat di hadapan Allah, Bapa kita, ialah mengunjungi yatim piatu dan janda-janda dalam kesusahan mereka, dan menjaga supaya dirinya sendiri tidak dicemarkan oleh dunia“. oiya ktnya definisi janda-janda yg di dalam Alkitab itu adalah wanita yg ditinggal mati oleh suaminya dan tetap menjaga kesendiriannya hingga umur 60 itu baru di sebut janda jd yah more or less kita harus care lah ma yatim piatu n jg janda, kek anak kecil yg pengamen2 itu jg termasup loh….

jadih apakah kita mo sungguh2 mjd sahabat Allah? seperti Tuhan sendiri telah menganggap kita sebagai sahabatNya?

Persahabatan Sejati

juwitharawung — Thu, 13 Mar 2008 07:10:30 +0000

*persahabatan sejati…..

Hanya… semenit diperlukan untuk mendapat sahabat baik… sejam untuk menghargainya… sehari untuk menyayanginya… tapi sepanjang hidup untuk melupakannya ,”bukan sepanjang hidup saja untuk melupakan orang2 yang qt sayangi tapi lebih dari itu, kehilangan adalah bagian dari hidup yang akan qt lalui tp apakah qt mampu memperjuangkannya?

seorang teman ataupun sahabat tidak pernah mengenal kata ‘melupakan’seorang sahabat tak akan pernah melupakan sahabatnya lagi, tapi mungkin karena jarak dan waktu yang membuat seseorang sejenak terlupakan,dam kesibukan untuk menggapai cita2,dan terus2 untuk memperbaiki diri itu yang membuat seolah waktu terasa sangat kurang, jadi jangan sekali-sekali menganggap seorang sahabat akan melupakan sahabatnya lagi…

seorang sahabat tidak mengenal kata melupakan,bukan kehidupan yang memiliki arti kalau kita ga’ mengalami kekecewaan, ataupun bahagia,mungkin butuh waktu untuk melupakan org yang qt sayangi,lebih baik waktu yang menjawab semuanya daripada hidup qt yang terus tenggelam dlm semua hal yg bs membuat hidup qt hancur.

mencintai tanpa syarat, berbicara tanpa perhatian, memberi tanpa alasan dan peduli tanpa pamrih..itu inti dr persahabatan sejati

Berilah waktu utk itu , kamu akan memberi keceriaan kepada seseorang atau mungkin mengubah hidup mereka kepada yang lebih baik.. thx for being my friend! I LOVE U FRIENDS….

Persahabatan adalah Kasih Sayang Tanpa Syarat

juwitharawung — Thu, 13 Mar 2008 07:01:12 +0000

Dalam menjalin sebuah persahabatan yang murni dan abadi ia memerlukan pengorbanan yang besar. Bila kita berkenalan dengan seseorang dan kita suka padanya maka kita pasti malu menjalin ikatan persahabatan yang kekal lama dengannya. Namun banyak dugaan dan rintangan yang akan mengiringi persahabatan itu sehinggakan ia boleh memusnahtan sebuah erti persahabatan.

Perubahan tanpa kompromi

Selama ini Mohsein ingatkan Rashdan adalah teman jati baginya. Mereka membesar bersama dan menghadiri sekolah yang sama.Mereka melalui saat gembira dan sedih bersama-sama. Mohsein masih ingat lagi bila Rashdan ditinggalkan oleh teman wanitanya. Mohseinlah tempat bagi Rashdan mengadu dan meluahkan perasaan kecewanya. Sebagai teman karib, Mohsein cuba memujuknya agar bertabah hati dan jangan terlalu bersedih.

Persahabatan erat antara Mohsein dan Rashdan amat bermakna bagi mereka berdua. Namun segala-galanya berubah dengan tiba-tiba. Rashdan sudah jarang menghubungi Mohsein lagi. Malah, ‘bayangnya’ pun sudah jarang kelihatan. Lalu Mohsein cuba mendapatkan jawapan daripadanya tapi Rashdan hanya diam membisu tanpa berkata apa-apa.

Mohsein rasa hairan melihat sikap Rashdan. Apakah kesilapan Mohsein yang menyebabkan Rashdan bersikap dingin terhadapnya? Mohsein bagaikan memerah otaknya mencari punca Rashdan bersikap begitu. Akhirnya, seorang teman Mohsein memberitahunya Rashdan berasa kecewa kerana Mohsein dapat pekerjaan baru. “Rashdan fikir kamu dah berubah sekarang dan tidak sama seperti dulu lagi.” kata teman itu. Jelas Rashdan adalah seorang yang tidak dapat sesuaikan diri dengan perubahan yang berlaku.

Dalam kehidupan harian, perubahan adalah sesuatu yang tidak boleh dielakkan. Walaupun kita tidak terfikir ia akan berlaku namun semuanya adalah di luar kawalan kita. Umpamanya dalam kes Mohsein yang rumit ini. Mohsein baru saja memulakan keria di pejabat baru dan kerianya memerlukan dia berkorban masa. Jadual keria Mohsein amat sibuk sehinggakan dia jarang ada masa bersosial.

Mohsein terkejut dengan sikap Rashdan yang tidak faham kedudukannya sekarang. “Dia yang menggalakkan aku memohon bekerja di sini tapi sekarang dia rasa lain pulak. Segala-galanya terjawab selepas tiga bulan aku dapat tahu Rashdan juga ada memohon kerja di tempat yang sama tapi dia gagal,” ujar Mohsein.

Perubahan besar dalam kehidupan boleh memberi kesan dan menggugat sebuah persahabatan. Ini termasuk perubahan dalam kerjaya, percintaan dan perpindahan rumah. Kita perlu faham hidup ini tidak statik. Perubahan ialah sebahagian daripada realiti dalam hidup. Persahabatan memerlukan flesikbel dan boleh menerima sesuatu perubahan yang berlaku.

Perubahan besar yang berlaku sering melibatkan emosi. Oleh itu, Mohsein berpendapat dia perlu meluangkan masa agar dapat bersama Rashdan walaupun dia sibuk. “Mungkin aku dapat berjumpa dengan Rashdan di hari minggu.” katanya.

Sifat-sifat sahabat yang baik

juwitharawung — Thu, 13 Mar 2008 06:56:47 +0000

SIFAT-SIFAT SEORANG SAHABAT BAIK

Orang yang mempunyai sahabat baik dan merupakan sahabat baik bagi
orang lain sesungguhnya adalah orang yang sangat kaya dan puas.

Persahabatan yang baik seharusnya menunjukkan ciri-ciri seperti
berikut ini :

1. Persahabatan yang baik tidak mementingkan diri sendiri.

Amsal 17:17 mengatakan bahwa,

“Seorang sahabat menaruh kasih setiap waktu.”

Karena itu persahabatan sejati tidak didasarkan pada syarat-
syarat yang berubah-ubah. Ada orang-orang yang berkata, “Saya

akan menjadi sahabatmu jika, atau apabila, atau sampai, atau

karena.” Semua ini adalah syarat-syarat dan syarat bisa berubah.

Tetapi sahabat sejati mengasihi setiap waktu. Seorang sahabat
yang berkata, “Aku mengasihimu jika” atau “Aku mengasihimu bila”

bukan sahabat seperti yang dilukiskan oleh Alkitab. Sahabat
sejati akan berkata, “Aku mengasihimu setiap waktu. Kasihku
tidak bersyarat dan tidak mementingkan diri sendiri.”

2. Persahabatan sejati bersifat teguh.

Kembali Amsal 17:17 berkata bahwa,

“Seorang sahabat menaruh kasih setiap waktu.”

Sebuah penerbitan Inggris menawarkan hadiah bagi orang yang
memberikan definisi terbaik tentang persahabatan. Sebuah definisi
yang tercantum dalam sayembara terhormat itu adalah: “Seorang
sahabat adalah orang yang menambah sukacita kita dan membagi
kesedihan kita.” Definisi lain berbunyi, “Seorang sahabat adalah
orang yang mengerti kita.” Tetapi definisi yang memenangkan
hadiah dalam sayembara itu adalah: “Seorang sahabat adalah orang
yang masuk pada saat dunia keluar.” Betapa benarnya definisi ini!

Jika Saudara ingin sungguh-sungguh mengetahui berapa banyak
sahabat yang Saudara miliki dan siapa mereka, buatlah kesalahan
dan lihatlah apa yang terjadi. Setelah Saudara mengetahui
kesulitan, coba lihat berapa banyak kawan Saudara yang masih
setia kapada Saudara. Persahabatan sejati itu teguh.

3. Persahabatan sejati bersedia berkorban.

Amsal 18:24 berkata,

“Ada teman yang mendatangkan kecelakaan, tetapi ada juga
sahabat yang lebih karib daripada seorang saudara.”

Persahabatan sejati itu mahal, tetapi memang sepadan dengan
nilainya. Kata Indian untuk sahabat berasal dari sebuah kata
gabungan yang berarti “orang yang memikul kesusahanku pada
pundaknya.” Jadi kalau saya ingin menjadi sahabat, saya harus
hidup dengan bersedia berkorban bagi orang yang menerima
persahabatan saya.

4. Persahabatan sejati bersifat menyucikan.

Amsal 27:17 berkata,

“Besi menajamkan besi, orang menajamkan sesamanya.”

Seorang sahabat sejati akan menjadikan Saudara orang yang lebih
baik. Persahabatan sejati membuat hidup Saudara lebih maju,
mempertajam kecerdasan Saudara dan membuat Saudara lebih giat.
Saudara akan menjadi orang yang lebih baik dan lebih berguna
karena persahabatan itu.

Persahabatan sejati tidak akan menumpulkan pengaruh Saudara atau
menumpulkan kerohanian Saudara. Seorang sahabat sejati adalah orang
yang cukup peduli sehingga ia akan menegur bila Saudara salah.

Alkitab berkata dalam Amsal 27:6,

“Seorang kawan memukul dengan maksud baik, tetapi seorang lawan
mencium secara berlimpah-limpah.”

Sanjungan bukan persahabatan. Orang yang suka menyanjung sama dengan
orang munafik. Seorang munafik mengatakan di belakang Saudara apa
yang tidak akan dia ucapkan di muka Saudara, tetapi seorang
penyanjung mengatakan di depan Saudara apa yang tidak akan ia
katakan di belakang Saudara. Seorang sahabat sejati sebaliknya, ia
bersifat jujur terhadap Saudara dan terhadap orang lain.

Persahabatan

juwitharawung — Thu, 13 Mar 2008 05:24:38 +0000

Persahabatan adalah istilah yang menggambarkan perilaku kerja sama dan saling mendukung antara dua atau lebih entitas sosial. Artikel ini memusatkan perhatian pada pemahaman yang khas dalam hubungan antar pribadi. Dalam pengertian ini, istilah “persahabatan” menggambarkan suatu hubungan yang melibatkan pengetahuan, penghargaan dan afeksi. Sahabat akan menyambut kehadiran sesamanya dan menunjukkan kesetiaan satu sama lain, seringkali hingga pada altruisme. selera mereka biasanya serupa dan mungkin saling bertemu, dan mereka menikmati kegiatan-kegiatan yang mereka sukai. Mereka juga akan terlibat dalam perilaku yang saling menolong, seperti tukar-menukar nasihat dan saling menolong dalam kesulitan. Sahabat adalah orang yang memperlihatkan perilaku yang berbalasan dan reflektif. Namun bagi banyak orang, persahabatan seringkali tidak lebih daripada kepercayaan bahwa seseorang atau sesuatu tidak akan merugikan atau menyakiti mereka.

Nilai yang terdapat dalam persahabatan seringkali apa yang dihasilkan ketika seorang sahabat memperlihatkan secara konsisten:

kecenderungan untuk menginginkan apa yang terbaik bagi satu sama lain.
simpati dan empati.
kejujuran, barangkali dalam keadaan-keadaan yang sulit bagi orang lain untuk mengucapkan kebenaran.
saling pengertian.

Seringkali ada anggapan bahwa sahabat sejati sanggup mengungkapkan perasaan-perasaan yang terdalam, yang mungkin tidak dapat diungkapkan, kecuali dalam keadaan-keadaan yang sangat sulit, ketika mereka datang untuk menolong. Dibandingkan dengan hubungan pribadi, persahabatan dianggap lebih dekat daripada sekadar kenalan, meskipun dalam persahabatan atau hubungan antar kenalan terdapat tingkat keintiman yang berbeda-beda. Bagi banyak orang, persahabatan dan hubungan antar kenalan terdapat dalam kontinum yang sama.

Akibat Pergaulan Bebas

juwitharawung — Thu, 13 Mar 2008 05:02:34 +0000

Tingginya Penderita HIV/AIDS Akibat Pergaulan Bebas
Kapanlagi.com – Tingginya kasus penyakit Human Immunodeficiany Virus/Acquired Immnune Deficiency Syndrome (HIV/AIDS), khususnya pada kelompok umur remaja, salah satu penyebabnya akibat pergaulan bebas.
Selain hilangnya kekebalan daya tubuh, pergaulan bebas juga dapat menyebabkan terjadinya kehamilan di luar nikah, kata Kepala BKKBN Propinsi Bali, I Gede Putu Abadi, MPA di Denpasar, Senin (24/10).

Dalam sambutan tertulis dibacakan Kepala Balai Latihan dan Pengembangan, Ida Bagus Wirama, SH ketika membuka pelatihan managemen pusat informasi dan konsultasi kesehatan reproduksi remaja bagi relawan dan pengelola, ia menyatakan, kondisi tersebut cukup memprihatinkan.

Hasil penelitian di 12 kota di Indonesia termasuk Denpasar menunjukkan 10-31% remaja yang belum menikah sudah pernah melakukan hubungan seksual.

Di kota Denpasar dari 633 pelajar Sekolah Menengah Tingkat Atas (SLTA) yang baru duduk di kelas II, 155 orang atau 23,4% mempunyai pengalaman hubungan seksual.

Mereka terdiri atas putra 27% dan putri 18%. Data statistik nasional mengenai penderita HIV/AIDS di Indonesia menunjukkan bahwa sekitar 75% terjangkit hilangnya kekebalan daya tubuh pada usia remaja.

Demikian pula masalah remaja terhadap penyalahgunaan narkoba semakin memprihatinkan, ujar Putu Abadi.

Berdasarkan data penderita HIV/AIDS di Bali hingga Pebruari 2005 tercatat 623 orang, sebagian besar menyerang usia produktif. Penderita tersebut terdiri atas usia 5-14 tahun satu orang, usia 15-19 tahun 21 orang, usia 20-29 tahun 352 orang, usia 30-39 tahun 185 orang, usia 40-49 tahun 52 orang dan 50 tahun ke atas satu orang.

Putu Abadi menambahkan, semakin memprihatinkan penderita HIV/AIDS memberikan gambaran bahwa, cukup banyak permasalahan kesehatan reproduksi yang timbul diantara remaja. Oleh sebab itu mengembangan model pusat informasi dan konsultasi kesehatan reproduksi remaja melalui pendidik (konselor) sebaya menjadi sangat penting.

“Pusat informasi dan konsultasi kesehatan reproduksi remaja menjadi model pemberdayaan masyarakat yang bertujuan menumbuhkan kesadaran dan peranserta individu memberikan solusi kepada teman sebaya yang mengalami masalah kesehatan reproduksi,” ujar Putu Abadi.

Pelatihan Managemen tersebut diikuti 24 peserta utusan dari delapan kabupaten dan satu kota di Bali berlangsung selama empat hari. (*/lpk)

AbOrSi

juwitharawung — Sat, 01 Mar 2008 00:22:04 +0000

ABORSI = MEMBUNUH KARYA ALLAH

Jakarta–bkkbn online; Pengguguran janin (aborsi) merupakan tindakan menghentikan karya Allah. Bahkan dapat dikatakan membunuh buah karya Allah. Karena itu Kristen secara tegas melarang aborsi.

Demikian pandangan Kristen tentang aborsi sebagaimana dimuat dalam buku ”Keluarga Bahagia Sejahtera dan Bertanggung Jawab Perspektif Agama Kristen”. Buku setebal 77 halaman ini diterbitkan oleh Persekutuan Gereja-Gereja di Indonesia bekerja sama dengan BKKBN dan UNFPA (Dana Kependudukan PBB).

”Setiap pelaku aborsi adalah pembunuh nyawa manusia di hadapan Allah. Aborsi adalah soal pencabutan nyawa manusia dan penumpahan darah insani ciptaan Allah,” ujar Pdt. Weinata Sairin MTh, wakil sekretaris umum Majelis Pekerja Harian Persekutuan Gereja-Gereja di Indonesia, dengan lebih tegas.

Manakala dalam sebuah keluarga yang sah terjadi kehamilan yang tidak direncanakan, menurut Weinata, janin tersebut harus mutlak dipelihara. ”Pewahyuan dalam Perjanjian Lama yang diwarisi dan diterima gereja memberikan bukti nyata, bahwa kehidupan dalam rahim dianggap kudus,” tutur Weinata.

Musa dalam (UI 28:2-6) menyatakan, ”Segala berkat ini akan datang kepadamu dan menjadi bagianmu, jika engkau mendengarkan suara Tuhan, Allahmu: … Diberkatilah buah kandunganmu…” (sara)

Protein

juwitharawung — Thu, 28 Feb 2008 05:16:54 +0000

Protein

A representation of the 3D structure of myoglobin showing coloured alpha helices. This protein was the first to have its structure solved by X-ray crystallography.

This article is about a class of biomolecules. For alternate uses, such as protein in nutrition, see Protein (disambiguation).

Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by a gene and encoded in the genetic code. Although this genetic code specifies 20 “standard” amino acids plus selenocysteine and – in certain archaea – pyrrolysine, the residues in a protein are sometimes chemically altered in post-translational modification: either before the protein can function in the cell, or as part of control mechanisms. Proteins can also work together to achieve a particular function, and they often associate to form stable complexes.

Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in every process within cells. Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. Proteins are also necessary in animals’ diets, since animals cannot synthesize all the amino acids they need and must obtain essential amino acids from food. Through the process of digestion, animals break down ingested protein into free amino acids that are then used in metabolism.

The word protein comes from the Greek word πρώτα (“prota”), meaning “of primary importance.” Proteins were first described and named by the Swedish chemist Jöns Jakob Berzelius in 1838. However, central role of proteins in living organisms was not fully appreciated until 1926, when James B. Sumner showed that the enzyme urease was a protein.^[1] The first protein to be sequenced was insulin, by Frederick Sanger, who won the Nobel Prize for this achievement in 1958. The first protein structures to be solved included hemoglobin and myoglobin, by Max Perutz and Sir John Cowdery Kendrew, respectively, in 1958.^[2]^[3] The three-dimensional structures of both proteins were first determined by x-ray diffraction analysis; the structures of myoglobin and hemoglobin won the 1962 Nobel Prize in Chemistry for their discoverers.

[edit] Biochemistry

Main articles: Amino acid and peptide bond

Resonance structures of the peptide bond that links individual amino acids to form a protein polymer.

Section of a protein structure showing serine and alanine residues linked together by peptide bonds. Carbons are shown in white and hydrogens are omitted for clarity.

Proteins are linear polymers built from 20 different L-α-amino acids. All amino acids possess common structural features, including an α carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. Only proline differs from this basic structure as it contains an unusual ring to the N-end amine group, which forces the CO–NH amide moiety into a fixed conformation.^[4] The side chains of the standard amino acids, detailed in the list of standard amino acids, have different chemical properties that produce three-dimensional protein structure and are therefore critical to protein function. The amino acids in a polypeptide chain are linked by peptide bonds formed in a dehydration reaction. Once linked in the protein chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen, and oxygen atoms are known as the main chain or protein backbone. The peptide bond has two resonance forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar. The other two dihedral angles in the peptide bond determine the local shape assumed by the protein backbone.

Due to the chemical structure of the individual amino acids, the protein chain has directionality. The end of the protein with a free carboxyl group is known as the C-terminus or carboxy terminus, whereas the end with a free amino group is known as the N-terminus or amino terminus.

The words protein, polypeptide, and peptide are a little ambiguous and can overlap in meaning. Protein is generally used to refer to the complete biological molecule in a stable conformation, whereas peptide is generally reserved for a short amino acid oligomers often lacking a stable three-dimensional structure. However, the boundary between the two is not well defined and usually lies near 20–30 residues.^[5] Polypeptide can refer to any single linear chain of amino acids, usually regardless of length, but often implies an absence of a defined conformation.

[edit] Synthesis

Main article: Protein biosynthesis

The DNA sequence of a gene encodes the amino acid sequence of a protein.

Proteins are assembled from amino acids using information encoded in genes. Each protein has its own unique amino acid sequence that is specified by the nucleotide sequence of the gene encoding this protein. The genetic code is a set of three-nucleotide sets called codons and each three-nucleotide combination stands for an amino acid, for example AUG stands for methionine. Because DNA contains four nucleotides, the total number of possible codons is 64; hence, there is some redundancy in the genetic code, with some amino acids specified by more than one codon. Genes encoded in DNA are first transcribed into pre-messenger RNA (mRNA) by proteins such as RNA polymerase. Most organisms then process the pre-mRNA (also known as a primary transcript) using various forms of post-transcriptional modification to form the mature mRNA, which is then used as a template for protein synthesis by the ribosome. In prokaryotes the mRNA may either be used as soon as it is produced, or be bound by a ribosome after having moved away from the nucleoid. In contrast, eukaryotes make mRNA in the cell nucleus and then translocate it across the nuclear membrane into the cytoplasm, where protein synthesis then takes place. The rate of protein synthesis is higher in prokaryotes than eukaryotes and can reach up to 20 amino acids per second.^[6]

The process of synthesizing a protein from an mRNA template is known as translation. The mRNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairing anticodon located on a transfer RNA molecule, which carries the amino acid corresponding to the codon it recognizes. The enzyme aminoacyl tRNA synthetase “charges” the tRNA molecules with the correct amino acids. The growing polypeptide is often termed the nascent chain. Proteins are always biosynthesized from N-terminus to C-terminus.

The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass, which is normally reported in units of daltons (synonymous with atomic mass units), or the derivative unit kilodalton (kDa). Yeast proteins are on average 466 amino acids long and 53 kDa in mass.^[5] The largest known proteins are the titins, a component of the muscle sarcomere, with a molecular mass of almost 3,000 kDa and a total length of almost 27,000 amino acids.^[7]

[edit] Chemical synthesis

Short proteins can also be synthesized chemically by a family of methods known as peptide synthesis, which rely on organic synthesis techniques such as chemical ligation to produce peptides in high yield.^[8] Chemical synthesis allows for the introduction of non-natural amino acids into polypeptide chains, such as attachment of fluorescent probes to amino acid side chains.^[9] These methods are useful in laboratory biochemistry and cell biology, though generally not for commercial applications. Chemical synthesis is inefficient for polypeptides longer than about 300 amino acids, and the synthesized proteins may not readily assume their native tertiary structure. Most chemical synthesis methods proceed from C-terminus to N-terminus, opposite the biological reaction.

[edit] Structure of proteins

Main article: Protein structure

Three possible representations of the three-dimensional structure of the protein triose phosphate isomerase. Left: all-atom representation colored by atom type. Middle: simplified representation illustrating the backbone conformation, colored by secondary structure. Right: Solvent-accessible surface representation colored by residue type (acidic residues red, basic residues blue, polar residues green, nonpolar residues white).

Most proteins fold into unique 3-dimensional structures. The shape into which a protein naturally folds is known as its native state. Although many proteins can fold unassisted simply through the structural propensities of their component amino acids, others require the aid of molecular chaperones to efficiently fold to their native states. Biochemists often refer to four distinct aspects of a protein’s structure:

Primary structure: the amino acid sequence
Secondary structure: regularly repeating local structures stabilized by hydrogen bonds. The most common examples are the alpha helix and beta sheet.^[10] Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule.
Tertiary structure: the overall shape of a single protein molecule; the spatial relationship of the secondary structures to one another. Tertiary structure is generally stabilized by nonlocal interactions, most commonly the formation of a hydrophobic core, but also through salt bridges, hydrogen bonds, disulfide bonds, and even post-translational modifications. The term “tertiary structure” is often used as synonymous with the term fold.
Quaternary structure: the shape or structure that results from the interaction of more than one protein molecule, usually called protein subunits in this context, which function as part of the larger assembly or protein complex.

NMR structures of the protein cytochrome c in solution show the constantly shifting dynamic structure of the protein. Larger version.

Proteins are not entirely rigid molecules. In addition to these levels of structure, proteins may shift between several related structures while they perform their biological function. In the context of these functional rearrangements, these tertiary or quaternary structures are usually referred to as “conformations,” and transitions between them are called conformational changes. Such changes are often induced by the binding of a substrate molecule to an enzyme’s active site, or the physical region of the protein that participates in chemical catalysis. In solution all proteins also undergo variation in structure through thermal vibration and the collision with other molecules, see the animation on the right.

Molecular surface of several proteins showing their comparative sizes. From left to right are: Antibody (IgG), Hemoglobin, Insulin (a hormone), Adenylate kinase (an enzyme), and Glutamine synthetase (an enzyme).

Proteins can be informally divided into three main classes, which correlate with typical tertiary structures: globular proteins, fibrous proteins, and membrane proteins. Almost all globular proteins are soluble and many are enzymes. Fibrous proteins are often structural; membrane proteins often serve as receptors or provide channels for polar or charged molecules to pass through the cell membrane.

A special case of intramolecular hydrogen bonds within proteins, poorly shielded from water attack and hence promoting their own dehydration, are called dehydrons.

[edit] Structure determination

Discovering the tertiary structure of a protein, or the quaternary structure of its complexes, can provide important clues about how the protein performs its function. Common experimental methods of structure determination include X-ray crystallography and NMR spectroscopy, both of which can produce information at atomic resolution. Cryoelectron microscopy is used to produce lower-resolution structural information about very large protein complexes, including assembled viruses;^[10] a variant known as electron crystallography can also produce high-resolution information in some cases, especially for two-dimensional crystals of membrane proteins.^[11] Solved structures are usually deposited in the Protein Data Bank (PDB), a freely available resource from which structural data about thousands of proteins can be obtained in the form of Cartesian coordinates for each atom in the protein.

Many more gene sequences are known than protein structures. Further, the set of solved structures is biased toward proteins that can be easily subjected to the conditions required in X-ray crystallography, one of the major structure determination methods. In particular, globular proteins are comparatively easy to crystallize in preparation for X-ray crystallography. Membrane proteins, by contrast, are difficult to crystallize and are underrepresented in the PDB.^[12] Structural genomics initiatives have attempted to remedy these deficiencies by systematically solving representative structures of major fold classes. Protein structure prediction methods attempt to provide a means of generating a plausible structure for proteins whose structures have not been experimentally determined.

[edit] Cellular functions

Proteins are the chief actors within the cell, said to be carrying out the duties specified by the information encoded in genes.^[5] With the exception of certain types of RNA, most other biological molecules are relatively inert elements upon which proteins act. Proteins make up half the dry weight of an Escherichia coli cell, whereas other macromolecules such as DNA and RNA make up only 3% and 20%, respectively.^[13] The set of proteins expressed in a particular cell or cell type is known as its proteome.

The enzyme hexokinase is shown as a simple ball-and-stick molecular model. To scale in the top right-hand corner are two of its substrates, ATP and glucose.

The chief characteristic of proteins that allows their diverse set of functions is their ability to bind other molecules specifically and tightly. The region of the protein responsible for binding another molecule is known as the binding site and is often a depression or “pocket” on the molecular surface. This binding ability is mediated by the tertiary structure of the protein, which defines the binding site pocket, and by the chemical properties of the surrounding amino acids’ side chains. Protein binding can be extraordinarily tight and specific; for example, the ribonuclease inhibitor protein binds to human angiogenin with a sub-femtomolar dissociation constant (<10^-15 M) but does not bind at all to its amphibian homolog onconase (>1 M). Extremely minor chemical changes such as the addition of a single methyl group to a binding partner can sometimes suffice to nearly eliminate binding; for example, the aminoacyl tRNA synthetase specific to the amino acid valine discriminates against the very similar side chain of the amino acid isoleucine.

Proteins can bind to other proteins as well as to small-molecule substrates. When proteins bind specifically to other copies of the same molecule, they can oligomerize to form fibrils; this process occurs often in structural proteins that consist of globular monomers that self-associate to form rigid fibers. Protein-protein interactions also regulate enzymatic activity, control progression through the cell cycle, and allow the assembly of large protein complexes that carry out many closely related reactions with a common biological function. Proteins can also bind to, or even be integrated into, cell membranes. The ability of binding partners to induce conformational changes in proteins allows the construction of enormously complex signaling networks.

[edit] Enzymes

Main article: Enzyme

The best-known role of proteins in the cell is their duty as enzymes, which catalyze chemical reactions. Enzymes are usually highly specific catalysts that accelerate only one or a few chemical reactions. Enzymes carry out most of the reactions involved in metabolism and catabolism, as well as DNA replication, DNA repair, and RNA synthesis. Some enzymes act on other proteins to add or remove chemical groups in a process known as post-translational modification. About 4,000 reactions are known to be catalyzed by enzymes.^[14] The rate acceleration conferred by enzymatic catalysis is often enormous – as much as 10¹⁷-fold increase in rate over the uncatalyzed reaction in the case of orotate decarboxylase (78 million years without the enzyme, 18 milliseconds with the enzyme).^[15]

The molecules bound and acted upon by enzymes are known as substrates. Although enzymes can consist of hundreds of amino acids, it is usually only a small fraction of the residues that come in contact with the substrate, and an even smaller fraction – 3-4 residues on average – that are directly involved in catalysis.^[16] The region of the enzyme that binds the substrate and contains the catalytic residues is known as the active site.

[edit] Cell signaling and ligand transport

A mouse antibody against cholera that binds a carbohydrate antigen.

Many proteins are involved in the process of cell signaling and signal transduction. Some proteins, such as insulin, are extracellular proteins that transmit a signal from the cell in which they were synthesized to other cells in distant tissues. Others are membrane proteins that act as receptors whose main function is to bind a signaling molecule and induce a biochemical response in the cell. Many receptors have a binding site exposed on the cell surface and an effector domain within the cell, which may have enzymatic activity or may undergo a conformational change detected by other proteins within the cell.

Antibodies are protein components of adaptive immune system whose main function is to bind antigens, or foreign substances in the body, and target them for destruction. Antibodies can be secreted into the extracellular environment or anchored in the membranes of specialized B cells known as plasma cells. Whereas enzymes are limited in their binding affinity for their substrates by the necessity of conducting their reaction, antibodies have no such constraints. An antibody’s binding affinity to its target is extraordinarily high.

Many ligand transport proteins bind particular small biomolecules and transport them to other locations in the body of a multicellular organism. These proteins must have a high binding affinity when their ligand is present in high concentrations, but must also release the ligand when it is present at low concentrations in the target tissues. The canonical example of a ligand-binding protein is hemoglobin, which transports oxygen from the lungs to other organs and tissues in all vertebrates and has close homologs in every biological kingdom.

Transmembrane proteins can also serve as ligand transport proteins that alter the permeability of the cell membrane to small molecules and ions. The membrane alone has a hydrophobic core through which polar or charged molecules cannot diffuse. Membrane proteins contain internal channels that allow such molecules to enter and exit the cell. Many ion channel proteins are specialized to select for only a particular ion; for example, potassium and sodium channels often discriminate for only one of the two ions.

[edit] Structural proteins

Structural proteins confer stiffness and rigidity to otherwise-fluid biological components. Most structural proteins are fibrous proteins; for example, actin and tubulin are globular and soluble as monomers, but polymerize to form long, stiff fibers that comprise the cytoskeleton, which allows the cell to maintain its shape and size. Collagen and elastin are critical components of connective tissue such as cartilage, and keratin is found in hard or filamentous structures such as hair, nails, feathers, hooves, and some animal shells.

Other proteins that serve structural functions are motor proteins such as myosin, kinesin, and dynein, which are capable of generating mechanical forces. These proteins are crucial for cellular motility of single celled organisms and the sperm of many sexually reproducing multicellular organisms. They also generate the forces exerted by contracting muscles.

[edit] Methods of study

Main article: Protein methods

As some of the most commonly studied biological molecules, the activities and structures of proteins are examined both in vitro and in vivo. In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function: for example, enzyme kinetics studies explore the chemical mechanism of an enzyme’s catalytic activity and its relative affinity for various possible substrate molecules. By contrast, in vivo experiments on proteins’ activities within cells or even within whole organisms can provide complementary information about where a protein functions and how it is regulated.

[edit] Protein purification

Main article: Protein purification

In order to perform in vitro analysis, a protein must be purified away from other cellular components. This process usually begins with cell lysis, in which a cell’s membrane is disrupted and its internal contents released into a solution known as a crude lysate. The resulting mixture can be purified using ultracentrifugation, which fractionates the various cellular components into fractions containing soluble proteins; membrane lipids and proteins; cellular organelles, and nucleic acids. Precipitation by a method known as salting out can concentrate the proteins from this lysate. Various types of chromatography are then used to isolate the protein or proteins of interest based on properties such as molecular weight, net charge and binding affinity. The level of purification can be monitored using various types of gel electrophoresis if the desired protein’s molecular weight and isoelectric point are known, by spectroscopy if the protein has distinguishable spectroscopic features, or by enzyme assays if the protein has enzymatic activity. Additionally, proteins can be isolated according their charge^[17] using electrofocusing.

For natural proteins, a series of purification steps may be necessary to obtain protein sufficiently pure for laboratory applications. To simplify this process, genetic engineering is often used to add chemical features to proteins that make them easier to purify without affecting their structure or activity. Here, a “tag” consisting of a specific amino acid sequence, often a series of histidine residues (a “His-tag“), is attached to one terminus of the protein. As a result, when the lysate is passed over a chromatography column containing nickel, the histidine residues ligate the nickel and attach to the column while the untagged components of the lysate pass unimpeded.

[edit] Cellular localization

Proteins in different cellular compartments and structures tagged with green fluorescent protein (here, white).

The study of proteins in vivo is often concerned with the synthesis and localization of the protein within the cell. Although many intracellular proteins are synthesized in the cytoplasm and membrane-bound or secreted proteins in the endoplasmic reticulum, the specifics of how proteins are targeted to specific organelles or cellular structures is often unclear. A useful technique for assessing cellular localization uses genetic engineering to express in a cell a fusion protein or chimera consisting of the natural protein of interest linked to a “reporter” such as green fluorescent protein (GFP). The fused protein’s position within the cell can be cleanly and efficiently visualized using microscopy, as shown in the figure opposite.

Through another genetic engineering application known as site-directed mutagenesis, researchers can alter the protein sequence and hence its structure, cellular localization, and susceptibility to regulation, which can be followed in vivo by GFP tagging or in vitro by enzyme kinetics and binding studies.

[edit] Proteomics and bioinformatics

Main articles: Proteomics and Bioinformatics

The total complement of proteins present at a time in a cell or cell type is known as its proteome, and the study of such large-scale data sets defines the field of proteomics, named by analogy to the related field of genomics. Key experimental techniques in proteomics include Mass Spectrometry, which allows rapid highthroughput identification of proteins and sequencing of peptides. protein microarrays, which allow the detection of the relative levels of a large number of proteins present in a cell, and two-hybrid screening, which allows the systematic exploration of protein-protein interactions. The total complement of biologically possible such interactions is known as the interactome. A systematic attempt to determine the structures of proteins representing every possible fold is known as structural genomics.

The large amount of genomic and proteomic data available for a variety of organisms, including the human genome, allows researchers to efficiently identify homologous proteins in distantly related organisms by sequence alignment. Sequence profiling tools can perform more specific sequence manipulations such as restriction enzyme maps, open reading frame analyses for nucleotide sequences, and secondary structure prediction. From this data phylogenetic trees can be constructed and evolutionary hypotheses developed using special software like ClustalW regarding the ancestry of modern organisms and the genes they express. The field of bioinformatics seeks to assemble, annotate, and analyze genomic and proteomic data, applying computational techniques to biological problems such as gene finding and cladistics.

[edit] Structure prediction and simulation

Complementary to the field of structural genomics, protein structure prediction seeks to develop efficient ways to provide plausible models for proteins whose structures have not yet been determined experimentally. The most successful type of structure prediction, known as homology modeling, relies on the existence of a “template” structure with sequence similarity to the protein being modeled; structural genomics’ goal is to provide sufficient representation in solved structures to model most of those that remain. Although producing accurate models remains a challenge when only distantly related template structures are available, it has been suggested that sequence alignment is the bottleneck in this process, as quite accurate models can be produced if a “perfect” sequence alignment is known.^[18] Many structure prediction methods have served to inform the emerging field of protein engineering, in which novel protein folds have already been designed.^[19] A more complex computational problem is the prediction of intermolecular interactions, such as in molecular docking and protein-protein interaction prediction.

The processes of protein folding and binding can be simulated using techniques derived from molecular dynamics, which increasingly take advantage of distributed computing as in the Folding@Home project. The folding of small alpha-helical protein domains such as the villin headpiece^[20] and the HIV accessory protein^[21] have been successfully simulated in silico, and hybrid methods that combine standard molecular dynamics with quantum mechanics calculations have allowed exploration of the electronic states of rhodopsins.^[22]

[edit] Nutrition

Further information: Protein in nutrition

Most microorganisms and plants can biosynthesize all 20 standard amino acids, while animals, (including humans) must obtain some of the amino acids from the diet.^[13] Key enzymes in the biosynthetic pathways that synthesize certain amino acids – such as aspartokinase, which catalyzes the first step in the synthesis of lysine, methionine, and threonine from aspartate – are not present in animals. The amino acids that an organism cannot synthesize on its own are referred to as essential amino acids. If amino acids are present in the environment, microorganisms can conserve energy by taking up the amino acids from their surroundings and downregulating their biosynthetic pathways.

In animals, amino acids are obtained through the consumption of foods containing protein. Ingested proteins are broken down through digestion, which typically involves denaturation of the protein through exposure to acid and hydrolysis by enzymes called proteases. Some ingested amino acids are used for protein biosynthesis, while others are converted to glucose through gluconeogenesis, or fed into the citric acid cycle. This use of protein as a fuel is particularly important under starvation conditions as it allows the body’s own proteins to be used to support life, particularly those found in muscle.^[23] Amino acids are also an important dietary source of nitrogen.

[edit] History

Further information: History of molecular biology

Proteins were recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy and others, distinguished by the molecules’ ability to coagulate or flocculate under treatments with heat or acid. Noted examples at the time included albumen from egg whites, blood, serum albumin, fibrin, and wheat gluten. Dutch chemist Gerhardus Johannes Mulder carried out elemental analysis of common proteins and found that nearly all proteins had the same empirical formula. The term “protein” to describe these molecules was proposed in 1838 by Mulder’s associate Jöns Jakob Berzelius. Mulder went on to identify the products of protein degradation such as the amino acid leucine for which he found a (nearly correct) molecular weight of 131 Da.

The difficulty in purifying proteins in large quantities made them very difficult for early protein biochemists to study. Hence, early studies focused on proteins that could be purified in large quantities, e.g., those of blood, egg white, various toxins, and digestive/metabolic enzymes obtained from slaughterhouses. In the late 1950s, the Armour Hot Dog Co. purified 1 kg (= one million milligrams) of pure bovine pancreatic ribonuclease A and made it freely available to scientists around the world.

Linus Pauling is credited with the successful prediction of regular protein secondary structures based on hydrogen bonding, an idea first put forth by William Astbury in 1933. Later work by Walter Kauzmann on denaturation, based partly on previous studies by Kaj Linderstrøm-Lang, contributed an understanding of protein folding and structure mediated by hydrophobic interactions. In 1949 Fred Sanger correctly determined the amino acid sequence of insulin, thus conclusively demonstrating that proteins consisted of linear polymers of amino acids rather than branched chains, colloids, or cyclols. The first atomic-resolution structures of proteins were solved by X-ray crystallography in the 1960s and by NMR in the 1980s. As of 2006, the Protein Data Bank has nearly 40,000 atomic-resolution structures of proteins. In more recent times, cryo-electron microscopy of large macromolecular assemblies and computational protein structure prediction of small protein domains are two methods approaching atomic resolution.

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Protein

Protein

Contents

[edit] Biochemistry

[edit] Synthesis

[edit] Chemical synthesis

[edit] Structure of proteins

[edit] Structure determination

[edit] Cellular functions

[edit] Enzymes

[edit] Cell signaling and ligand transport

[edit] Structural proteins

[edit] Methods of study

[edit] Protein purification

[edit] Cellular localization

[edit] Proteomics and bioinformatics

[edit] Structure prediction and simulation

[edit] Nutrition

[edit] History