Nucleic acid chemistry
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Transcript of Nucleic acid chemistry
Nucleic Acid
Nucleotides are precursors of nucleic acid DNA & RNA
Nucleic acids were first isolated by Friedrich Miescher in 1869.
suga r base
sug a r base
phospha te
sug ar ba se
phospha te
su ga r base
phospha te
su ga r base
phospha te
Nucleoside
Nucleotides
Nucleic acids
1 23
2
1
Nitrogenous Bases
Purines (double-ring structures)
A and G
Pyrimidines (single-ring structures)
C, T, and U
hyperphysics.phy-astr.gsu.edu
PURINES AND PYRIMIDINES
Purines and pyrimidines are AROMATIC HETEROCYCLIC COMPOUNDS contain both carbon and other elements (hetero atoms).
NUCLEOSIDE• Nucleosides are derivatives of purines and pyrimidines that
have a sugar linked to a ring nitrogen.
The sugar is linked to the heterocyclic base via a β-N-glycosidic bond, almost always to N-1 of a pyrimidine or to N-9 of a purine.
NUCLEOTIDE STRUCTUREPHOSPATE SUGAR
Ribose or Deoxyribose
NUCLEOTIDE
BASEPURINES PYRIMIDINES
Adenine (A)Guanine(G)
Cytocine (C)Thymine (T)Uracil (U)
Important Analogs of Purine Pyrimidine &Nucleotides
• 1.Allopurinol-used in treatment of gout
• 2.Azathioprine-suppress immunological rejection during transplantation
• 3.Arabinosyladenine-used in treatment of neurological diseases
• 4.Arabinosylcytosine-used in cancer therapy
• 5.Drugs used in AIDS are sugars modified synthetic nucleotide Analogs
THE SUGAR-PHOSPHATE BACKBONE
• The nucleotides are all orientated in the same direction
• The phosphate group joins the 3rd Carbon of one sugar to the 5th Carbon of the next in line.
P
P
P
P
P
P
ADDING IN THE BASES
• The bases are attached to the 1st Carbon
• Their order is important It determines the genetic information of the molecule
P
P
P
P
P
P
G
C
C
A
T
T
DNA IS MADE OF TWO STRANDS OF POLYNUCLEOTIDE
P
P
P
P
P
P
C
G
G
T
A
A
P
P
P
P
P
P
G
C
C
A
T
T
Hydrogen bonds
OTHER FORMS OF DNA STRUCTURE
BENT DNA
TRIPLE STRANDED DNA
FOUR STRANDED DNA
IT IS BELIEVED THAT SUCH STRUCTURES ARE IMPORTANT FOR MOLECULAR RECOGNITION OF DNA BY PROTEINS AND ENZYMES
The Nucleosome -DNA (146 bp) wrapped around octamer of core histone proteins (+ linker DNA = ~200 bp)
ORGANISATION OF DNA
• Much more abundant than DNA
• Single stranded structure
• Contains ribose (DNA 2’-deoxy ribose)
• Contains uracil base• Does not obey Chargaff ’s rule
• Susceptible to alkaline hydrolysis
• Retains all information of DNA
• Specific RNA for specific functions
• Structure similar to A-form DNA
• 3 major types• mRNA : 5-10%
• tRNA: 10-20 %
• rRNA: 50-80 %