HA HC ACID AMIN V PROTEINBs. Chi Mai

Ha hc acid amin v proteinMc tiu:Trnh by c cu to, phn loi acid aminTrnh by c cc lin kt trong phn t protein, cc bc cu trc ca proteinTrnh by c tnh cht l ha ca protein v ng dngTrnh by c vai tr sinh hc ca protein

HA HC ACID AMINnh ngha: Acid amin l nhng cht hu c trong phn t c hai nhm chc carboxyl v amin cng gn vi carbon Trong t nhin c 20 aa thng gp cu to nn proteinPhn loi:Da vo gc R chia lm 5 nhm: Acid amin c gc R khng phn cc, R phn cc nhng khng tch in, R nhn thm, R base, R acid.

Cu trc v c tnh ca acid amin a-carbon l carbon bt i (tr glycine)Ti pH 7.0 acid amin l ion lng tnh Acid amin c cu trc hnh t din

ng phn quang hc ca acid aminCc sinh vt ch tng hp v s dng L- acid amin

Acid amin c gc R khng phn cc (6 aa)Prolin (pro, P) vng imino acid

Glycin (gly, G) l acid amin duy nht khng c ng phn quang hc, khng k nc

Alanin (ala, A) R = nhm methyl

Valin (Val, V)

Leucin (Leu, L)

Isoleucin (Ile, I) - 2 carbon bt i Tnh k nc

Acid Amin c gc R cha nhn thm (3 aa)Tt c rt k ncGc R l nhn thmHp th UV ti 280 nmPhenylalanin (Phe, F) Tyrosin (Tyr,Y) -OH c kh nng ion ha (pKa = 10.5)Tryptophan (Trp, W) 2 vng gm c vng indol

Acid amin acid (2 aa)Cha nhm carboxyl (tnh acid yu hn nhm a-carboxyl)Tch in m ti pH sinh lAspartat (Asp)Glutamat (Glu)

Acid amin kim (3 aa)a ncTch in dng ti pH sinh lHistidin (His) nhn imidazol tn ti di dng ion dng, l acid amin duy nht c kh nng m pH sinh l.Lysin (Lys) tch in dng ti pH 7.0 Arginin (Arg) - guanidinium ion lun tch in dng, l acid amin c tnh kim nht

pKa = 6.0

Acid amin c gc R phn cc nhng khng tch in (6 aa)R phn cc, a nc, c th to lin kt H

Hydroxyl ca Ser v Thr c kh nng ion ha yu

Serin (Ser, S) ging Ala thm nhm -OH

Threonin (Thr, T) c 2 carbon bt i

Asparagin (Asn, N) amid ca acid aspartic

Glutamin (Gln, Q) amid ca acid glutamicMethionin (Met, M) start amino acid, rt k nc, S tn ti di dng lin kt thioeste

Cystein (Cys,C) S dng sulfhydroyl (thiol), quan trng trong to cu disulfur tnh acid yu

Tnh cht ca acid aminTnh cht lng tnhPhn ng ninhydrin: khi un nng acid amin phn ng vi ninhydrin to phc mu xanh tm (tr prolin cho mu vng)Cc phn ng mu c hiu ca acid amin

Ha hc proteinPhn loi:Theo hnh dngProtein hnh si: t l chiu di/chiu rng > 10. L cc protein cu trcProtein hnh cu: t l chiu di/ chiu rng < 10. L cc protein chc nngPhn loi: Theo cu toProtein thun: Ch do aa cu to lnProtein tp: ngoi aa cn c thnh phn khc khng phi aa (nhm ngoi)

CU TRC CA PROTEINCc loi lin kt trong phn t protein:Lin kt peptidLin kt disulfurLin kt hydroLin kt ion (lin kt mui, lin kt tnh in)Tng tc k nc

Polyme ca cc acid amin: s to thnh lin kt Peptid

Lin kt peptid l mt lin kt na iLin kt peptid c c tnh ca mt lin kt na i.O ca nhm carbonyl tch in dng mt phn, N ca nhm amin tch in dng mt phn.

Lin kt Peptid c cu trc phngCu trc na i ca lin kt peptid ngn cn s quay t do xung quanh lin kt C-N; gi lin kt C-N trn cng mt phng v gn vi cc nguyn t O v H. Cc mt phng lin kt ny c th xoay xung quanh nguyn t Ca.Lin kt ng ha tr, bn vng.

Cu trc lp th hay gp ca lin kt peptid (ng phn)Cu hnhTrans;Hay gp trong t nhin v thun li v khng gianCu hnh Cis ;Him gp v khng thun li v khng gian

Cc lin kt bnh n cu trc ca protein1. Tnh in/ion3. Tng tc k nc2. Lin kt Hydrogen 4. Lin kt Disulfur

Cc bc cu trc ca proteinCu trc bc mt ca protein l do s lng, loi v trnh t sp xp cc acid amin trong chui polypeptid to nn.Lin kt quyt nh cu trc bc 1 l lin kt peptid.Cc protein khc nhau c cu trc bc mt khc nhau

Phn loi cu trc bc haiCu trc xon (Alpha helix)

Cu trc gp np beta (b-sheet)

Quai v im quay

Cu trc xon alpha (a-helix) Linus Pauling v Robert Corey a ra u tin vo nm 1951 Max Perutz xc nhn trong keratin Ph bin trong proteins Lin kt H bnh n cu trc bc 2

Xon phi hay xon tri Xon tri him gp trong t nhin!

Xon phi a-helixS gc aa/ vng xon: 3.6 Chiu cao 1 gc aa: 1.5 AngstromChiu cao 1 vng xon: 3.6 x 1.5A = 5.4 Angstrom Nguyn t H ca nhm amin to lin kt hydro vi oxy ca nhm carbonyl cch 4 aa, hnh thnh quai c 13 nguyn t.

Cu trc xon alpha

Quai v im quayQuai:Thng cha cc gc a nc.Tm thy trn b mt protein.Ni xon alpha v gp np beta.im quay:Quai c < 5 aa c gi l im quayCc im quay beta rt hay gp

Cu trc tm beta (gp np beta)Cng do Pauling v Corey a ra nm 1951 Cc chui c th song song hoc i songChiu di ca mi gc aa: 3.47 Angstroms vi cc chui i song

3.25 Angstroms vi cc chui song song

Mi chui trong cu trc tm beta c th xem nh xon helix vi 2 gc aa / vng xon

Gp np BetaCu trc gp np Beta to thnh t nhiu chui beta sp xp cnh nhau. Cc chui c th song song hoc i song. Cu trc tm i song n nh hn.

Cc chui bn trong gp np betaCc chui bn (gc R ca aa) quay ln trn hoc xung di mt phng ca tm beta. 2 n 15 chui beta/tm betaMi chui khong 6 amino acid

Chui bn trong cu trc a-helixCc gc R ca aa hng ra pha ngoi ca trc xonCc aa c chui bn cng knh t gp trong alpha-helixGlycine v proline lm mt n nh cu trc alpha-helix

Cu trc bc baTt c cc protein hnh cu c cu trc bc 3.Cc phn t protein c cu trc bc 2 b v gp li to cu trc khng gian 3 chiu hnh cu.Myoglobin l protein c trong t bo c. Cc lin kt H, lin kt ion, tng tc k nc v cu disulfur bnh n cu trc bc 3

Cu trc bc 4Ch cc protein c t 2 chui Polypeptid tr ln mi c th c cu trc bc bn.

Cc lin kt H, lin kt ion, tng tc k ncbnh n cu trc bc bn

Tnh cht l ha ca proteinTnh cht lng tnh: Ty theo pH mi trng m protein tn ti di dng tch in m, dng hay trung ha v in.pH ng in ca protein l pH mi trng m ti protein tn ti di dng trung ha v in.Tnh ha tan: Protein hnh cu tan trong nc hay dung dch mui long to dung dch keo. Dung dch keo bn vng nh s tch in cng du ca cc tiu phn keo v lp o nc.

Tnh cht l ha ca proteinTnh kt ta: Loi b lp o nc v trung ha in tch th protein kt ta.S bin tnh: cu trc bc 2, 3,4 b ph v (cc lin kt b ph v tr lin kt peptid).

Chc nng sinh hc ca proteinVai tr cu trcVai tr xc tc: enzymVai tr vn chuyn:Vai tr bo vVai tr vn ngVai tr iu haCc vai tr khc

The observed kinetic energy of a particle is an average of contributions from the entire space covered by the wavefunction. Sharply curved regions contribute a high kinetic energy to the average; slightly curved regions contribute only a small kinetic energy.