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Polimerhoi biologi–safedaho

Dar bayni moddahoi organikii hujayra safedaho miqdoran va az rui ahamiyat joi avvalro ishgol menamoyand. Dar hayvonot taqriban 50%-i massai khushki hujayraho ba safedaho rost meoyad. Dar organizmi odam 5 mln. tipi molekulahoi safedagi vomekhurand, ki na faqat bayni hamdigar, inchunin az safedahoi digar organizmho niz farq mekunand.

Bo vujudi hamin qadar gunoguni va murakkabii sokht safedaho hamagi az 20 aminokislotahoi mukhtalif tarkib yoftaand. Formulai umumii onho chunin ast:

PolimerhoDar qismi chapi molekula guruhi amin joygir shudaast, ki on khosiyati asosro zohir menamoyad; az tarafi rost – guruhi karboksil SOON – guruhi kislotagi joygir ast, ki baroi tamomi kislotahoi organiki khos meboshad. Az in ru, fahmidan dushvor nest, ki aminokislotaho-payvastagihoi amfoteri buda, ba khosiyathoi khimiyavii ham asos va ham kislota sohiband. In sababi bayni

yakdigar tasiri mutaqobila namudani onho megardad. Molekulai aminokislotaho bo ham payvast shuda, bayni guruhi karboksili (SOON) va amini) band ba vujud meorand. CHunin bandro bandi kovalenti, vale dar in mavrid onro bandi peptidi menomand:

Payvast shudani du aminokislota dar yak molekula dipeptid, se aminokislota-tripeptid nomida meshavad. Payvastagii iborat az 20 aminokislota va boqimondai az on beshtari aminokislotagiro-polipeptid menomand.

Aminokislotaho sokhti umumii aniq dorand, lekin azhamdigar tanho bo sokhti radikal (R) farq mekunand, ki khele gunogun ast. Masalan, dar aminokislotai alanin radikaloddi–SN3 meboshad, radikali aminokislotai sistein boshad, sulfur–SN2SH dorad; digar aminokislotaho radikalhoi beshtar murakkabro sohiband.

Safedahoe, ki az organizmhoi zindai hayvonot, rastani va mikroorganizmho judo karda shudaand, az sadho va bazan az hazorho kombinatsiyai (bo hamdigar yakjoyashavii) 20 aminokislotai asosi iboratand. Tartibi paydarham (paiham)

payvastshavii boqimondai aminokislotaho ba mavjudiyati miqdori ziyodi molekulai safedaho dar tabiati zinda imkoniyat dodaast; hamai onho az hamdigar farq mekunand.

Paydarham joygirshavii aminokislotahoro dar zanjiri (silsilai) polipeptidi strukturai yakumini safeda menomand. Vale molekulai safeda dar namudi zanjiri boqimondahoi aminokislotagi, ki paiham bayni yakdigar bo bandi peptidi payvast shudaand, hanuz qobiliyati ijro kardani funksiyai makhsusro nadorad. Baroi in, tashkili beshtar balandi strukturai molekulai safeda zarur ast. Tavassuti ba vujud omadani bandhoi gidrogeni bayni boqimondai guruhhoi karboksil va aminoguruhhoi aminokislotahoi gunogun

molekulai safeda namudi spirali sathash chindor (purchin) qabul menamoyad ( – struktura). In strukturai duyumini safeda meboshad (rasmhoi 3.1, 3.2). Ammo vay aksaran vaqt baroi qabuli faoliyati khosi biologi kofi nest.

Aksaran, tanho, vaqte ki molekulai safeda strukturai seyumin zohir menamoyad, dar on holat vazifai kataliza tor yo yagon vazifai digarro ijro karda metavonad. Strukturai seyumini safeda ba tufayli tasiri mutaqobilai radikalho, qisman radikalhoi aminokislotai sistein, ki sulfur dorand, ba vujud meoyad. Atomhoi sulfuri du aminokislota, ki az yakdigar dar andak masofa dar zanjiri polipeptidi joygirand, payvast shuda, bo nom bandi disulfidi S-S ba vujud meorand. Ba tufayli chunin tasiri mutaqobila spirali safedagi pechutob khurda, shakli kura yo tubcha (kalobacha)-ro megirad.

Qobiliyati joygir shudani spirali polipeptidi dar chunin kura strukturai seyumini safeda nomida meshavad. Bisyor safedaho, ki strukturai seyumin zohir menamoyand, vazifai biologii khudro dar hujayra ijro karda metavonand. Lekin baroi ba amal ovardani baze funksiyahoi organizm ishtiroki safedahoi darajai tashkil yobiashon boz ham balandtar zarur ast. Hamin guna darajai balandi tashkilyobii sokhti molekulai safedaro strukturai chorumin menomand.

Strukturai chorumini safeda az muttahidshavii funksionalii yakchand (du, se va beshtar) molekulai safeda iborat ast, ki strukturai seyuminro zohir menamoyand. Misoli hamin guna safedai murakkab gemoglobin meboshad. Molekulai on az chor molekulai bayni yakdigar payvast iborat ast. Misoli digar gormoni gadudi zeri meda-insulin shuda metavonad, ki az du komponent (qismi tarkibi) iborat me- boshad. Dar tarkibi strukturai chorumini baze safedaho, ba gayr az qismi safedagi, komponenthoi gunoguni gayri safedagi niz mavjudand. Az jumla, safedai dar bolo nomburda – gemoglobin payvastagii geterosiklii murakkab dorad, ki ba tarkibi on ohan dokhil ast.

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