Nucleic Acid Chemistry

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Nucleic Acid Chemistry
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contents
1 introduction 2 compositiong 3 Structure 4
nucleic acid and nucleotide property
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?Introduction
1.discovery and development of nucleic acid

• 1868, Fridrich Miescher first isolated nuclein
  from pyocyte(???).

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1944 O.Avery confirmed DNA is hereditary
substance.
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                            A Erwin Chargaff in the late 1940s. They found that the four nucleotide bases in DNA

•  Rosalind Franklin and Maurice Wilkins showed in
  the early 1950s that DNA produces a
  characteristic x-ray diffraction pattern

1953 J.Watson F.Crick discovered DNA double
helix.
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1968, Nirenberg found the genetic code .

Marshall W. Nirenberg
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2. classification, distributing and function of
nucleic acids
DNA RNA
laying Nucleus90,mitochondrium, autoplast, plasmid. Nucleus, cytochyma
function Having genetic information and deciding genotye of body. Jion in genetic expression.
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? composition of nucleic acid
DNA RNA
base Purine bases ??? Adenine??? (A) Adenine??? (A)
base Purine bases ??? Guanine??? (G) Guanine??? (G)
base Pyrimidine bases ??? Cytosine??? (C) Cytosine??? (C)
base Pyrimidine bases ??? Thymine????(T) Uracil???(U)
pentose D-2-deoxyribose D-2-???? D-ribose D-??
acid phosphoric acid ?? phosphoric acid ??
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Nucleotide
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pentose
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Base
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7
6
1
8
3
7
1
1
6
8
9
2
3
3
1
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Ribonucleoside
cytidine??CR
guanine deoxyriboside ????dGR
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The linkage of base with ribose(2-deoxyribose)
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Deoxyribonucleotides The product of
deoxyribonucleoside linking of phosphoric acid at
5 position.
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ribonucleotides
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Important nucleotides
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minor bases
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? structure of nucleic acid
1? structure of DNA
(1) The primary structure The primary
structure of a nucleic acid is its covalent
structure and nucleotide sequence.
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The primary structure
DNA was formed by linking of
deoxynucleotides with phosphodiester bond at 3
position of one deoxynucleotide and 5 position
of another deoxynucleotide.
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(2) Secondary structure
Double-stranded helix

• Characteristic
• The two strands are antiparallel.
• The chain, phosphoric acid and deoxyribose,
• locate lateral of the helix, but bases are in
  
• the helix.
• Pair strictly A to T, G to C.
• A turn contains 10 nucleotides, with height
• 3.4nm. Width 2.0nm.
• Form a major groove and a minor groove.
• Rotating right-handed.
• The maintaining force of the structure is
• hydrogen-bond.

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Pairs bases
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The Nobel Prize in Physiology or Medicine 1962
(1953)
Watson and Crick
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Versatility of DNA double helix
A-DNA is favored when DNA is dehydrated. Major
and minor grooves are similar in width.
B-DNA is the conformation normally found inside
cells.
Z-DNA is favored in certain G/C-rich sequences.
No grooves left handed helix
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Versatility of DNA double helix
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forces
two sets of forces, as described earlier
1. hydrogen bonding between complementary
base pairs 2. base-stacking interactions.
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(3) Tertiary structure of DNA----supercoil
Further coil of the DNA double helix.
(positive supercoil)
(negative supercoil)
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(4) Function of DNA
(1) Containing genetic information, as the
template of gene duplication , DNA
finally directs protein biosynthesis. As a
result, keeping hereditary characters of
body. (2) Gene refer to a segment of DNA chain
which posseses a special biological
function.
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2. spatial structure and function of RNA
RNAs in animal cell
Nuclus and cytochyma mitochondrium function
????RNA rRNA mt rRNA Component of ribosome
??RNA mRNA mt mRNA Template of protein synthesis
??RNA tRNA mt tRNA Transport amino acids
????RNA HnRNA Precursor of mature mRNA
??RNA SnRNA Jion in hnRNA splicing and transporting
???RNA SnoRNA Processing and modifying of rRNA
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(1) mRNA --messenger RNA

• 5capm7GpppNm-
• 3Poly A tailAn n20200
• Single chain
• half life time from munits to hours

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In prokaryotes a single mRNA molecule may
code for one or several polypeptide chains.
If it carries the code for only one
polypeptide, the mRNA is monocistronic if it
codes for two or more different polypeptides, the
mRNA is polycistronic. In eukaryotes,
most mRNAs are monocistronic. mRNAs transcribed
from DNA are always somewhat longer than needed
simply to specify the code for the polypeptide
sequence(s). The additional noncoding
RNA includes sequences that regulate protein
synthesis .
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(2) tRNA --transfer RNA
Secondary structure
? Stem-loop structure, cloverleaf pattern????. ?
3 loop and 1 arm DHU loop, anticoden loop,
Tfloop, AA arm. ? Anticoden and CCA-OH 3end. ?
Contain rare bases 10-20.
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tRNA tertiary structure a inverse L like.
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tRNA functions as a amino acid transfer in
protein biosynthesis.
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(3) rRNA --ribosomal RNA

• Weight 80 of total RNA in a cell.
• Flower like.
• Component of ribosome.
• procaryote5S,16S,23S
• eukaryote 18S,5S,5.8S,28S

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? nucleic acid and nucleotide property
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1. Ultraviolet absorption

• Nucleic acids get their maximum
• absorption at 260nm.
• DNA solution A260/A2801.8
• RNA solution A260/A280 2.0
• OD2601.0, equal to 50µg/ml DS DNA,
• 40µg/ml SS DNA or RNA.

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• hyperchromic effect
• The large increase in light absorption at 260 nm
  occurring as a double-helical DNA is melted
  (unwound).
• hypochromic effect
• The close interaction between stacked bases in a
  nucleic acid has the effect of decreasing the
  absorption of UV light relative to a solution
  with the same concentration of free nucleotides.
  This is called the hypochromic effect.

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2. DNA denaturation --the double
chain change into single chain
Methods heat, acid, base, urea, acetone?
Result OD260?, viscosity?, activity lose.
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Tm --melting temperature, ?????,????,refer to
the middle point of temperature range of DNA
thermal denaturation .

• The temperature of 50 double chain undoing.
• Tm69.30.41(GC)

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Renaturation and hybridization
Renaturation the single DNA chains recover their
natural double helix structure. Annealing??
renaturation of thermal denatural DNA, by way of
slow cooling.
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Hybridization??phenomenon of single chain DNA or
RNA bind the chain different origin in
renaturation process.