Different possible mechanism for generation of optical activity of hemoproteins in the Soret region are reconsidered. The heme undecapeptide of cytochrome c does not contain aromatic amino acid residues, so its considerable optical activity cannot be due to coupling of heme pi pi * transitions with those of aromatic residues. CD data for the heme undecapeptide and for ferrimyoglobin and some of their complexes with small molecules are presented and critically compared. Symmetrically coordinated imidazole complexes show rotational strengths of the same magnitude as those of corresponding nonsymmetrically coordinated compounds. Inherent chirality in the bound heme is inferred to be a significant source of optical activity in the heme undecapeptide. Theoretical calculations based upon a molecular dynamics simulation support this proposal. Coupled oscillator interactions with the peptide pi pi * transitions and with the high-energy transitions in the peptide groups and thioether sulfurs, as modeled by polarizabilities, also make significant contributions. These same mechanisms must also be considered in hemoproteins in general.

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The kinetics and reaction mechanism of the catalytic polymerization of methacrylic acid were investigated in aqueous solution. At pH 3-5-3-6, the overall reaction was found to be of first order with respect t o the monomer and t o vary as the square root of the catalyst concentration. From the decrease in reaction velocity with increasing pH (up t o pH 6, a t which the reaction velocity is practically zero), i t was concluded, that, t o a first approximation, only the non-ionized monomer takes part in the reaction. The true velocity constant K O for undissociated monomer was found to be (1-84 j, 0.08) x I O -~ sec.-1 a t 75" C and for a catalyst concentration of 0.98 g./Ioo ml. The weight average degree of polymerization was determined a t different pH values. The overall activation energy was measured in the temperature range 55-75' C and found t o be 10.8 & 0.3 kcal./mole. Chloride ions exert a strong inhibitory effect on the polymerization a t pH values below 2-5. This effect is not shown by sulphate and nitrate ions. A mechanism for the reaction in agreement with the experimental data obtained has been suggested. * Part of a thesis submitted by G. Blauer t o the Senate of the Hebrew University, Jerusalem, in partial fulfilment of the requirements for the degree of Doctor of Philosophy.