BIOM20001 Lecture Notes - Lecture 3: Leucine, Valine, Indole
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One or two methylenes capped by an amide group
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Asparagine (Asn, N)
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Glutamine (Gln, Q)
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Asn and Gln are not chemically reactive. They are polar. They share H-bond acceptors/donors.
Deamidate to Asp and Glu
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Uncharged polar side chains (amides)
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Hardly ever in this deionised form.
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Serine (Ser, S)
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Thr has an extra chiral centre. It has a methyl group so is polar and non-polar
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Threonine (Thr, T)
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Ser and Thr are not very chemically reactive. Are polar. H-bond donor and acceptor.
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Uncharged polar side chains (hydroxyls)
Phenylalanine (Phe, F)
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Aromatic side chains
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Document Summary
One or two methylenes capped by an amide group. It has a methyl group so is polar and non-polar. Ser and thr are not very chemically reactive. Reactive only under extreme conditions (not relevant to life). Even though ph10 is much higher than physiological ph, phenolate can exist at active site where other reactive groups can stabilize it. This plot shows how good each amino acid is good at absorbing light of different wavelengths. In general conjugated double bonds absorb uv light and produce fluorescent emission. Histidine doesn"t absorb appreciably even though it"s aromatic. Aromatic side chains (phe, tyr, trp): responsible for most uv absorbance and fluorescence properties of proteins. Extent and geometry of conjugated double bond systems cause spectral differences. Useful for the detection of proteins in solution. Spectral properties are sensitive to their immediate environment. Useful probes of protein structure. e. g. trp buried vs. exposed or trp aqueous vs liquid.
