BIOCHEMISTRY1NEUCLEIC

ACIDSCONTENTS24.1

Two

Nucleic

Acids: DNA

and

RNA4.2

Propertie

of

nucleotides

核苷酸4.3

Primary

Structure

of

Nucleic

Acids核酸的一級結(jié)構(gòu)4.4

Secondary

Structure

and

tertiaryStructureof

Nucleic

Acids核酸的二級結(jié)構(gòu)和三級結(jié)構(gòu)4.5

Stability

of

Secondary

andTertiaryStructure核酸的二級結(jié)構(gòu)和三級結(jié)構(gòu)的穩(wěn)定性4.2

NucleotidesNucleotides

=

Base

+Sugar

+

PhosphateNucleoside=

Sugar

+Base

(nophosphate)PRdRPbasebaseRibose

ordeoxyribose(核糖或脫氧核糖）4adenine（腺嘌呤）urecil（尿嘧啶）thymine（胸腺嘧啶）cytosine（胞嘧啶）guanine（鳥嘌呤）PurinebasesPyrimidine

Bases5Standard

Nucleotides：65’-adenosine

monophosphate

5’-AMP

（

5’-腺苷酸）5’-guanosine

monophosphate

5’-GMP

（5’-鳥苷酸）5’-cytidine

monophosphate5’-CMP

（

5’-胞苷酸）5’-uridine

monophosphate

5’-UMP

（

5’-脲苷酸）5’-

deoxyadenosine

monophosphate5’-dAMP（5’-脫氧腺苷酸）5’-

deoxyguanosine

monophosphate5’-dGMP（5’-脫氧鳥苷酸）5’-deoxycytidine

monophosphate

5’-dCMP

（5’-脫氧胞苷酸）5’-deoxythymidine

monophosphate）

5’-dTMP（5’-脫氧胸腺苷酸7Minor

Bases

or

Modified

bases(稀有堿基或修飾堿基)8Nucleotide

polyphosphate多磷酸核苷8

NDPs

（

5’-nucleotide

diphosphate

5’-核苷二磷酸）8

NTPs

（

5’-nucleotide

triphosphate

5’-核苷三磷酸）ATP9Cyclic

Nucleotides10CoA、NAD+（P）and

FADCo-enzyme

A（CoA）Nicotinamide

adenine

dinucleotide

（NAD+）煙酰胺腺嘌呤二核苷酸、Flavin

Adenine

Dinucleotide

（FAD）黃素腺嘌呤二核苷酸11NAD12NADP13FAD14Nucleotide

propertics1.

Dissociation

in

waterThe

phosphate

group

of

a

nucleotide

acts

as

a

strong

acid

(pKa

1),The

amine

groups

of

thepurine

and

pyrimidine

bases

can

beprotonated.152.Tautomerizationof thebasesThe

bases

cantautomerize(互變異構(gòu)）;

that

is,

the

bases

canredistribute

positions

ofhydrogens

and

doublebonds16Unusual base

pair見于酵母苯丙氨酰tRNA171-methyladenine

=TNucleotide

properticsSpectrumNucleotidesabsorb

lightstrongly

inthenear-ultravioletregion

of

thespectrum.19ε260（X104）20AMP1.54GMP1.17CMP0.75dTMP0.92UMP0.99.Biological

functions

ofnucleotides211、The

monomeric

units

of

nucleic

acids2、Energy

carrier：ATP、GTP、CTP、UTP3、signals

：cAMP、cGMP4、coenzymes：FAD、NAD、CoA4.3

Primary Structure

ofNucleic

AcidsThe

primary

structure

is

the

sequence

ofnucleosidemonophosphatesDirectionality

：5’

3’IndividualitypGGTA——,pGpGpTpA——,

GGTA——pGGTA（OH）22Significance

of

PrimaryStructureGenetic

informationstored

innucleotidesequence

of

DNAGene

is

aparticularDNA

sequence23DNA

isgeneticsubstance.Avery,MacLeod,McCartyHershey

and

Chase

-

Bacteriophage

T2transfers

DNA

tobacteria254.4

Secondary structure

ofDNA26The

secondary

structurerefers

to

the

shapea

nucleic

acid

assumes

as

a

result

of

theprimary

structure.B-DNA

:

predominant

form

in

theaqueousenvironment

of

the

cellA-DNAZ-DNA

: purine/pyrimidine

tracts11/

0.23nm10/

0.34nm12/

0.38nmSecondarystructureof

DNAMajor

groove27Minorgroove28Structure

of

B-DNA29—

The

two

chains

in

the

double

helix

areantiparallelPhosphate

groups

link

together

the

sugarbackbone

via

phosphodiester

bonds.The

bases

on

the

two

chains

pair

in

acomplementary

fashion.

A=T，G=CHydrogen

bonds

between

bases

hold

thedouble

helix

together.

(A=T，G≡C)—B-DNA:d=

2nm，pitch

=

3.4nm

,

10bp

/

turnofthe

helixDNA

base

pair30DNA

base

pair31DNA

basepairPrictice:Write

thesequence

.Thediscovery

of DNA

doublehelixChargaff's

Rule

(A=T,G=C

in

DNA)Franklin,

Wilkins:X-rayDiffractionRefined

Structure33Watson,

Crick34Significance

of

DNA

doublehelixsemi-conservative

modelofDNA

replication35Meselsonand

Stahlexperiment195836Application

of

ComplementarityDNA半保留復制Moleculehybridization核酸分子雜交實驗37Unusual

Secondary

Structuresof

DNAPalindromes(回文結(jié)構(gòu)）

Cruciform

formation

inpalindrome

sequencesGGCGCGCCCCGCGCGG38H-DNApurines/pyrimidinesononestrand?39404.5

Tertiary structure

of

DNA41Tertiary

structure

refers

to

large-scalefolding

in

a

linear

polymer

that

is

at

ahigherorder

than

secondary

structure.

Thetertiary

structureis

the

specific

three-dimensional

shape

into

which

an

entirechain

is

folded.Tertiary structure

of

DNA42Circular

DNAand

SupercoilingCircular

DNAsSupercoiling

:Positive(+)----additional

twists

addedbeyond

thenormalamount

for

linear

DNAnegative

(-)----reducednumbers

of

twistscompared

tolinearDNA.43Supercoiling44Twists(T,纏繞數(shù)):The

total

number

of

times

the

two

strands

of

the

helix

cross

over

eachother,

excludingwrithing.

Twist

is

a

measure

of

how

tightly

the

helixiswound.Writhes

(W,扭曲數(shù)):The

number

of

times

the

helix

as

awholecrosses

over

itself-that

is,the

number

of

superhelical

turns

that

arepresentLinking

number

(L,連接數(shù)):The

total

number

of

times

twostrands

of

a

DNA

helix

cross

each

other

by

means

of

either

twist

orwritheL

=

T

+

WThe

superhelical

density

:L/L0,

where

L0

is

the

linking

numberof

the

DNA

in

its

unstrained

(relaxedstate).Besides

writhing,

unwindingDNA,cruciform

formation

(via

palindromes),

triplehelix

formation

(H-DNA),

andZ-DNAformation,

can

all

reduce

superhelicaltension,

too.46Ethidium

bromide(溴乙錠)change

DNA

supercoil47problem

set481.

計算一個260bps的環(huán)狀DNA在松弛態(tài)和w=-2的L和超螺旋密度。松弛態(tài)：L=T=260/10=26超螺旋：T=26；L=T+W=26+（-2）=24；σ=-2/24=-0.08(已知自然界存在大多數(shù)DNA分子的superhelical

density（超螺旋密度）是-0.06，一個10000bpDNA分子，假定是B型構(gòu)像，將形成多少圈超螺旋？3.為什么DNA傾向形成負超螺旋而不是正超螺旋？RNA49tRNA504.6 The

Biological

Functions

ofNucleic

Acids511、Genome2、Transcription3、Translation:rRNA(ribosome:

Rizyme,

Structure)mRNAtRNA分子生物學中心法則5253M1RNAand

SRPM1RNA

：是E.coli的RNaseI的組成成分，該酶參與轉(zhuǎn)錄的RNA加工。SRP:

信號識別顆粒M1RNA4.7 Stability

of

Nucleic

AcidSecondary

and

Tertiary

Structure55Stability

and

DenaturationDenaturation:The

electrostatic

repulsion

of

the

negative

charges

on

thephosphate

groups.The

higher

entropy

of

the

denatured

state

(thedenaturedform

has

more

possible

conformations

than

thedoublehelix

form,

so

the

denatured

form

has

greater

randomness).Stability:hydrogen

bondsThe

van

der

Waals

interactions

between

the

planarbases56Factors

favoring

dissociation

ofdouble

helices

to

random

coils1、Hypochromism-

absorption

of

light

bybases

reduced

when

inhelix=denaturationcauses

increaseinabsorbance

of

light

at260nm.MeltingTemperature(Tm)：57The

factorsaffecting

onTm：①G-C（0.15mol/LNaCl//0.15mol/L

sodium

citrate）Tm=69.3+0.41（G+C）②DNA

purity③pH,

58問題591、如何保存DNA？A.

無水乙醇中；b.純水中；c.

75%乙醇中；2、應該如何配制DNA溶液，可使其比較穩(wěn)定？A.純水配制；b.

1mol/LNaCl配制；c.0.01mol/LNaCl配制；d.

0.5mol/LNaOH配制。溶解度：溶于水酸堿性：生理pH帶負電荷分子量和形狀：DNA108