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Biochem (Acid/Base (Isoelectric point (pI): pH where avg. charge for all…

- - - - ΔG= ΔG0' + RTlnQ
        where Q (mass action quotient) = [C]^c[D]^d/ [A]^a[B]^b
        
        If at eq. (ΔG=0), Q= Keq so 0= -RTlnKeq
        
        Keq= e^-ΔG0/ RT remember to keep J or KJ consistent, T in Kelvin, and R= 8.314 J/K*mole or 0. 008314 KJ
      - ΔG0' : standard state, all solutes at 1M, except [H+]= 10^-7 M and [H2o]=55.5 M, but it never changes so it cancels out to 1
    - - At equilibrium, ΔG=0, so ΔH=TΔS
- - - - Pauling figured out α-helix by folding paper so angles of amides were correct. From this he figured out the peptides/turn
      - Right handed, n=3.6 res/turn, p=5.4 A/turn
      - Helix-macrodipole: (+) charge on N-terminus, (-) charge on C-terminus
      - Side chains point out on L-isomers
      - Optimized VDW packing, the middle of the helice is all main chain atoms with no space inside
      - Heptad repeats: 7 A.A.'s appear together and are repeated throughout sequence
    - - Parallel:
        N---->C
        ';,;'';,;';, kinked (weaker) h-bonds
        N---->C
      - Antiparallel:
        N---->C
        : : : : :
        C<----N optimized h-bonds
- - - - Cysteine is titratable (pKa=8), can form di-sulfide bond with itself (important for protein structure), found at protein core
      - Serine and Threonine (pka=13) found on protein surface
    - - Glycine: most flexible A.A.
      - All have Carbon R groups that make them hydrophobic, found inside of protein shielded by water
    - - Planar, absorb UV light at 280 nm
      - Tryptophan, Phenylalanine are hydrophobic, weakly acidic
    - - (+) charge mostly, surface of protein
      - Histidine: pka=6-7, close to physiological pH so good for catalysis, metal binding, buffer
      - Lysine pka=10
        Arginine pka= 12.5
    - - Glutamic and Aspartic Acid pka= 4
    - - insulin?