Chok Biochem 3rd Shift Reviewer Nucleic Acid

CHEMISTRY OF NUCLEIC ACIDS • • • •

Nucleoproteins – proteins + nucleic acid Found in all animal and plant tissues DNA – polymers of nucleotides linked via phosphodiester bonds Information carrying molecules or catalysts

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Melting Point - @ Tm – 50% helix opened; ↓ Tm = renaturation Long Range interaction between A and C

Functions: Energy stores, Portions of coenzymes, Mediators / 2° messengers, Allosteric effects on enzymes, Activated intermediates Nucleic Acids • ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), polynucleotides

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Nucleotide = phosphate ester linkage @ OH group with nucleoside = nitrogenous base + sugar (ribose/deoxyribose) Nitrogenous Bases o Limited solubility in water o Exhibit tautomerism (keto or enol forms), keto mre stable o Aromatic = absorbs UV

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tRNA – AA carriers o clover-leaf 2° structure o 5’ terminal PO4 group, 3’ terminal OH (7 base pairs, AA stem) o D arm – dihydrouridine, loop o Anticodon arm – 5 base pairs, loop o TψC arm – has pseudouridine

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mRNA - translation o 5’ end with 7-methyl guanlylic acid (5’ to 5’ triphosphate linkage) o Polyadenylic tail o Leader sequences and trailer sequences o Eukaryotic mmRNA – monocistronic

Pyrimidines: thymine (T, DNA only) / cytosine (C) / uracil (U, RNA only); numbering counter-clockwise from 10 o clock, then clockwise from 1 o clock in smaller ring

Sugars o Ribose (for RNA) or deoxyribose (for DNA) o Connected via glycosidic linkage @ N1 Pyr + N9 Pur Nucleoside (-idine) Uridine Cytidine Thymidine Adenosine Guanosine

Nucleotide ( phosphate / -ylic acid) Uridine Phosphate / uridylic acid Cytidine Phosphate / cytidylic acid Thymidine Phosphate / thymidylic acid Adenosine Phosphate / adenylic acid Guanosine Phosphate / guanylicacid

DNA

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Purines: adenine (A) / guanine (G) bases; numbering clockwise from 6 o’clock

Nomeclature Base Uracil Cytosine Thymine Adenine Guanine

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RNA

Watson and Crick – double helix structure = 2 complementary polynucleotide chains Adenine base H bonded to Thymine, Guanine to Cystosine Nucleotide linkage – phosphodiester bond between 3’ OH and 5’ OH Predominant B form: right-handed, 20 A diameter, 10 base pairs per turn, 36° twist per base pair, 34A helix poitch, 3.4 helix rise, wide and deep major groove, narrow and deep minor groove Chargaff’s Rule: equal number of T and A, and G and C Antiparallel, complementary base pairing Base pair stability: van der Waals, hydrophobic effect Meselson-Stahl Experiment – semi-conservative DNA replication

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rRNA – ribosomal, for translation o multimolecular aggregates of protein and RNA o heavy + light subunits o Large (60S) = 28S, 5.8S, 5S o Light (40S) = 18S small nuclear RNA o highly conserved, 60-300 nucleotides o form protein complexes