Peb tsab xov xwm yuav mob siab rau kev kawm txog cov khoom ntawm cov khoom uas yog lub hauv paus ntawm qhov tshwm sim ntawm lub neej hauv ntiaj teb. Protein molecules muaj nyob rau hauv cov ntaub ntawv tsis-cellular - kab mob, yog ib feem ntawm lub cytoplasm thiab organelles ntawm prokaryotic thiab nuclear hlwb. Ua ke nrog cov nucleic acids, lawv tsim cov khoom ntawm kev xeeb tub - chromatin thiab tsim cov khoom tseem ceeb ntawm nucleus - chromosomes. Kev taw qhia, lub tsev, catalytic, tiv thaiv, lub zog - qhov no yog cov npe ntawm kev ua haujlwm lom neeg uas cov protein ua. Lub physicochemical zog ntawm cov proteins yog lawv muaj peev xwm yaj, precipitate, thiab ntsev tawm. Tsis tas li ntawd, lawv muaj peev xwm ntawm denaturing thiab yog, los ntawm lawv cov tshuaj xwm, amphoteric compounds. Cia peb tshawb nrhiav cov khoom ntawm cov protein ntxiv.
Ntau hom protein monomers
20 hom α-amino acids yog cov qauv ntawm cov protein. Ntxiv rau cov hydrocarbon radical, lawv muaj NH 2- amino pawg thiab COOH-pawg carboxyl. Cov pab pawg ua haujlwm txiav txim siab cov kua qaub thiab cov yam ntxwv ntawm cov protein monomers. Yog li ntawd, nyob rau hauv cov organic chemistry, cov tebchaw ntawm cov chav kawm no yog hu ua amphoteric tshuaj. Hydrogen ions ntawm pawg carboxyl hauv cov molecule tuaj yeem raug cais tawm thiab sib koom ua ke rau cov amino pawg. Qhov tshwm sim yog ib qho ntsev sab hauv. Yog hais tias muaj ntau pawg carboxyl nyob rau hauv lub molecule, ces cov compound yuav acidic, xws li glutamic los yog aspartic acid. Yog hais tias cov amino pawg predominate, cov amino acids yog qhov yooj yim (histidine, lysine, arginine). Nrog rau qhov sib npaug ntawm pawg ua haujlwm, cov tshuaj peptide muaj cov tshuaj tiv thaiv nruab nrab. Nws tau raug tsim los tias muaj tag nrho peb hom amino acids cuam tshuam dab tsi cov yam ntxwv ntawm cov proteins yuav muaj. Lub physicochemical zog ntawm cov proteins: solubility, pH, macromolecule nqi, yog txiav txim los ntawm tus piv ntawm acidic thiab yooj yim amino acids.
Yam dab tsi cuam tshuam rau kev solubility ntawm peptides
Cia peb tshawb nrhiav txhua yam tsim nyog uas cov txheej txheem ntawm hydration lossis kev daws cov protein macromolecules nyob ntawm. Cov no yog: spatial configuration thiab molecular hnyav, txiav txim los ntawm tus naj npawb ntawm cov amino acid residues. Nws kuj yuav siv sij hawm mus rau hauv tus account qhov piv ntawm polar thiab non-polar qhov chaw - radicals nyob rau saum npoo ntawm cov protein nyob rau hauv lub tertiary qauv thiab tag nrho cov nqi ntawm polypeptide macromolecule. Tag nrho cov khoom saum toj no ncaj qha cuam tshuam rau solubility ntawm cov protein. Cia wb mus saib lawv.
Globules thiab lawv lub peev xwm los hydrate
Yog tias cov qauv sab nraud ntawm peptide muaj cov duab kheej kheej, ces nws yog txoj cai los tham txog nws cov qauv globular. Nws yog ruaj khov los ntawm hydrogen thiab hydrophobic bonds, nrog rau lub zog ntawm electrostatic attraction ntawm oppositely them qhov chaw ntawm macromolecule. Piv txwv li, hemoglobin, uas nqa cov pa oxygen molecules los ntawm cov ntshav, hauv nws daim ntawv quaternary muaj plaub ntu ntawm myoglobin, koom ua ke los ntawm heme. Cov ntshav proteins xws li albumins, α- thiab ϒ-globulins yooj yim cuam tshuam nrog cov ntshav plasma. Insulin yog lwm globular peptide uas tswj cov ntshav qabzib hauv cov tsiaj thiab tib neeg. Lub hydrophobic qhov chaw ntawm xws li peptide complexes nyob rau hauv nruab nrab ntawm lub compact qauv, thaum lub hydrophilic qhov chaw nyob rau ntawm nws nto. Qhov no muab lawv nrog kev khaws cia ntawm cov khoom nyob hauv cov kua nruab nrab ntawm lub cev thiab muab lawv tso rau hauv ib pawg ntawm cov dej-soluble proteins. Qhov tshwj xeeb yog globular proteins uas tsim cov qauv mosaic ntawm daim nyias nyias ntawm tib neeg thiab tsiaj hlwb. Lawv cuam tshuam nrog glycolipids thiab yog insoluble nyob rau hauv lub intercellular kua, uas ua kom lawv lub luag hauj lwm barrier nyob rau hauv lub cell.
Fibrillar peptides
Collagen thiab elastin, uas yog ib feem ntawm lub dermis thiab txiav txim siab nws firmness thiab elasticity, muaj ib tug filamentous qauv. Lawv muaj peev xwm ncab, hloov lawv qhov chaw configuration. Fibroin yog ib qho protein ntau uas ua los ntawm silkworm larvae. Nws muaj cov qauv luv fibers, muaj cov amino acids nrog ib qho me me thiab molecular ntev. Cov no yog, ua ntej ntawm tag nrho cov, serine, alanine thiab glycine. Nwspolypeptide chains yog taw qhia nyob rau hauv qhov chaw nyob rau hauv ntsug thiab kab rov tav cov lus qhia. Cov tshuaj belongs rau cov qauv polypeptides thiab muaj cov txheej txheem txheej. Tsis zoo li globular polypeptides, solubility ntawm cov protein uas muaj cov fibrils yog tsawg heev, txij li cov hydrophobic radicals ntawm nws cov amino acids nyob rau saum npoo ntawm macromolecule thiab tshem tawm cov polar solvent particles.
Keratins thiab nta ntawm lawv cov qauv
Xav txog cov pab pawg ntawm cov txheej txheem ntawm cov proteins ntawm fibrillar daim ntawv, xws li fibroin thiab collagen, nws yog ib qho tsim nyog yuav tsum nyob ntawm ib pab pawg neeg ntxiv ntawm peptides dav dav hauv cov xwm txheej - keratins. Lawv ua lub hauv paus rau tej qhov chaw ntawm tib neeg thiab tsiaj lub cev xws li plaub hau, rau tes, plaub, ntaub plaub, hooves thiab claws. Dab tsi yog keratin nyob rau hauv cov nqe lus ntawm nws cov qauv biochemical? Nws tau raug tsim los tias muaj ob hom peptides. Tus thawj muaj daim ntawv ntawm ib tug kauv theem nrab qauv (α-keratin) thiab yog lub hauv paus ntawm cov plaub hau. Lwm qhov yog sawv cev los ntawm nruj txheej txheej fibrils - qhov no yog β-keratin. Nws tuaj yeem pom nyob rau hauv qhov nyuaj ntawm lub cev ntawm cov tsiaj: hooves, noog beaks, nplai ntawm cov tsiaj reptiles, claws ntawm predatory mammals thiab noog. Dab tsi yog keratin, raws li qhov tseeb tias nws cov amino acids, xws li valine, phenylalanine, isoleucine, muaj ntau cov hydrophobic radicals? Nws yog cov protein insoluble hauv dej thiab lwm cov kuab tshuaj polar uas ua haujlwm tiv thaiv thiab kev ua haujlwm.
Kev cuam tshuam ntawm pH ntawm nruab nrab ntawm tus nqi ntawm cov protein polymer
Ua ntej peb tau hais tias pawg ua haujlwm ntawm cov proteinmonomers - amino acids, txiav txim siab lawv cov khoom. Peb tam sim no ntxiv tias tus nqi ntawm cov polymer kuj nyob ntawm lawv. Ionic radicals - carboxyl pawg ntawm glutamic thiab aspartic acids thiab amino pawg ntawm arginine thiab histidine - cuam tshuam rau tag nrho cov nqi ntawm cov polymer. Lawv kuj coj txawv txawv hauv acidic, nruab nrab lossis alkaline daws. Lub solubility ntawm cov protein kuj nyob ntawm cov yam ntxwv no. Yog li, ntawm pH <7, cov tshuaj muaj qhov ntau tshaj ntawm hydrogen protons, uas inhibits kev tawg ntawm carboxyl, yog li tag nrho cov nqi zoo ntawm cov protein molecule nce.
Kev sib sau ntawm cations hauv cov protein kuj nce ntxiv nyob rau hauv cov ntaub ntawv ntawm cov tshuaj nruab nrab nruab nrab thiab nrog ntau dhau ntawm arginine, histidine thiab lysine monomers. Nyob rau hauv ib qho chaw alkaline, cov nqi tsis zoo ntawm polypeptide molecule nce, vim tias qhov ntau ntawm hydrogen ions yog siv los tsim cov dej molecules los ntawm kev khi cov pab pawg hydroxyl.
Yam uas txiav txim siab solubility ntawm cov proteins
Cia peb xav txog qhov xwm txheej uas tus lej ntawm qhov zoo thiab qhov tsis zoo ntawm cov protein helix yog tib yam. Qhov pH ntawm qhov nruab nrab hauv qhov no yog hu ua isoelectric point. Tag nrho cov nqi ntawm peptide macromolecule nws tus kheej dhau los ua xoom, thiab nws cov solubility hauv dej los yog lwm yam hnyav hnyav yuav tsawg. Cov kev cai ntawm txoj kev xav ntawm electrolytic dissociation hais tias solubility ntawm ib yam khoom nyob rau hauv ib tug polar solvent uas muaj dipoles yuav siab dua, qhov ntau polarized hais ntawm cov yaj compound. Lawv kuj piav qhia txog yam uas txiav txim siab txog kev solubilityCov proteins: lawv cov ntsiab lus isoelectric thiab dependence ntawm hydration los yog kev daws teeb meem ntawm peptide ntawm tag nrho cov nqi ntawm nws macromolecule. Feem ntau cov polymers ntawm cov chav kawm no muaj ntau tshaj ntawm -COO- pawg thiab muaj cov kua qaub me ntsis. Ib qho kev zam yuav yog yav dhau los hais txog daim nyias nyias cov proteins thiab peptides uas yog ib feem ntawm cov tshuaj nuclear ntawm heredity - chromatin. Cov tom kawg yog hu ua histones thiab tau hais cov yam ntxwv tseem ceeb vim muaj coob tus amino pawg hauv cov saw hlau polymer.
Kev coj tus cwj pwm ntawm cov protein hauv qhov hluav taws xob
Rau lub hom phiaj siv tau, nws feem ntau yuav tsum tau cais, piv txwv li, cov ntshav proteins rau hauv feem lossis ib tus neeg macromolecules. Txhawm rau ua qhov no, koj tuaj yeem siv lub peev xwm ntawm cov khoom siv hluav taws xob los ntawm cov khoom siv hluav taws xob kom txav mus los ntawm qee qhov ceev rau cov electrodes hauv qhov hluav taws xob. Ib qho kev daws teeb meem uas muaj peptides ntawm ntau qhov sib txawv thiab tus nqi yog muab tso rau ntawm cov cab kuj: ntawv lossis ib lub gel tshwj xeeb. Los ntawm kev hla hluav taws xob impulses, piv txwv li, los ntawm ib feem ntawm cov ntshav plasma, txog li 18 feem ntawm tus neeg cov proteins tau txais. Ntawm lawv: txhua hom globulins, nrog rau cov protein albumin, uas tsis yog tsuas yog cov khoom tseem ceeb tshaj plaws (nws suav txog li 60% ntawm cov ntshav plasma peptides), tab sis kuj tseem ua lub luag haujlwm tseem ceeb hauv cov txheej txheem osmosis. thiab ntshav ncig.
Yuav ua li cas ntsev concentration cuam tshuam rau cov protein solubility
Lub peev xwm ntawm peptides tsim tsis tsuas yog gels, foams thiab emulsions, tab sis kuj yog cov cuab yeej tseem ceeb uas qhia txog lawv cov yam ntxwv ntawm lub cev. Piv txwv li, yav dhau los kawmalbumins pom nyob rau hauv endosperm ntawm cereal noob, mis nyuj thiab ntshav cov ntshav sai sai tsim aqueous daws nrog ib tug concentration ntawm nruab nrab ntsev, xws li sodium chloride, nyob rau hauv thaj tsam li ntawm 3 mus rau 10 feem pua. Siv cov piv txwv ntawm tib cov albumins, ib tus tuaj yeem paub qhov kev cia siab ntawm cov protein solubility ntawm ntsev concentration. Lawv yaj zoo nyob rau hauv ib qho unsaturated tov ntawm ammonium sulfate, thiab nyob rau hauv ib tug supersaturated tov lawv precipitate reversibly thiab, nrog ib tug ntxiv txo nyob rau hauv cov ntsev concentration los ntawm ntxiv ib feem ntawm dej, restore lawv hydration plhaub.
Cov lus piav qhia saum toj no cov tshuaj tiv thaiv ntawm peptides nrog kev daws cov ntsev tsim los ntawm cov kua qaub muaj zog thiab alkalis yog hu ua s alting tawm. Nws yog ua raws li cov txheej txheem ntawm kev sib cuam tshuam ntawm cov pab pawg ua haujlwm ntawm cov protein nrog ntsev ions - hlau cations thiab anions ntawm acid residues. Nws xaus nrog kev poob nqi ntawm peptide molecule, txo qis hauv nws lub plhaub dej, thiab adhesion ntawm cov protein ntau. Yog li ntawd, lawv los nag, uas peb yuav tham tom qab.
nag xob nag cua thiab denaturation
Acetone thiab ethyl cawv ua kom lub plhaub dej nyob ib puag ncig cov protein hauv cov qauv tertiary. Txawm li cas los xij, qhov no tsis suav nrog qhov nruab nrab ntawm tag nrho cov nqi ntawm nws. Cov txheej txheem no hu ua nag lossis daus, solubility ntawm cov protein yog txo qis, tab sis tsis xaus nrog denaturation.
Peptide molecules hauv lawv lub xeev yog qhov nkag siab zoo rau ntau qhov chaw ib puag ncig, piv txwv li, raukub thiab concentration ntawm tshuaj compounds: ntsev, acids los yog alkalis. Txhim kho qhov kev txiav txim ntawm ob qho tib si ntawm cov ntsiab lus no ntawm isoelectric taw tes ua rau kev puas tsuaj tag nrho ntawm stabilizing intramolecular (disulfide txuas, peptide bonds), covalent thiab hydrogen bonds hauv polypeptide. Tshwj xeeb tshaj yog sai sai nyob rau hauv xws li mob, globular peptides denature, thaum tag nrho lawv cov physicochemical thiab lom zog.
