The recently implemented second-order perturbation theory based on a complete active space self-consistent field reference function has been extended by allowing the Fock-type one-electron operator, which defines the zeroth-order Hamiltonian to have nonzero elements also in nondiagonal matrix blocks. The computer implementation is now less straightforward and more computer time will be needed in obtaining the second-order energy. The method is illustrated in a series of calculations on N2, NO, O2, CH3, CH2, and F−.

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These results suggest that CSF Ng is a novel AD biomarker that may be used to monitor synaptic degeneration, and correlates with the rate of cognitive decline in prodromal AD.

Six closely related antibacterial proteins, attacins A‐F, were isolated from the hemolymph of immunized pupae of the Cecropia moth, Hyalophora cecropia. Chromatofocusing separated attacins A‐F, with isoelectric points between 5.7 and 8.3. Immunological experiments show that the attacins constitute antibacterially active forms of the previously isolated inducible immune protein P5. Their mol. wts., 20‐23 K, are similar to that of protein P5, but significantly lower than 28 K found for preP5 synthesized in vitro (see accompanying paper). The six attacins can be divided into two groups according to their amino acid composition and amino‐terminal sequences, attacins A‐D constitute a basic group and attacins E and F an acidic one. Within each group the forms are very similar. The attacins efficiently killed Escherichia coli and two other Gram‐negative bacteria isolated from the gut of a silk worm but they did not act on other Gram‐positive and Gram‐negative bacteria tested. Only growing cells of E. coli were attacked; cells suspended in phosphate buffer were inert. Besides the cecropins and lysozyme, the attacins represent a third class of antibacterial proteins in the humoral immune system of H. cecropia.

Multiconfigurational second-order perturbation theory is tested for the calculation of molecular structure and binding energies. The scheme is based on the Complete Active Space ( C A S ) SCF method, which gives a proper description of the major features in the electronic structure, independent of its complexity, accounts for all near degeneracy effects, and includes full orbital relaxation. Remaining dynamic electron correlation effects are in a subsequent step added using second-order perturbation theory with the CASSCF wave function as the reference state ( C A S P T~) .The approach is applied to the calculation of equilibrium geometry and atomization energies for 27 benchmark molecules containing first-row atoms (the "Gl" test). Large atomic natural orbital (ANo)-type basis sets are applied (5s4p3d2ffor Li-F and 3s2pld for H). It is shown that the CASS-C F / C A S P T~ approach is able to predict the equilibrium geometry with an accuracy better than 0.01 A for bond distances and 0"-2" for bond angles. Calculated atomization energies are underestimated with between 3 and 6 kcal/mol times the number of extra electron pairs formed. The error in the heat of reaction for a number of isogyric reaction (no difference in number of pairs) varies between -2.5 and +1.0 kcal/mol. The same type of accuracy is obtained in calculations for excited states. T h e molecules Bz, Cz, FO, FOO, and FOOF have also been studied. Results for the first three molecules are in accordanc: with those of the benchmark molecules. T h e F O bond distance in F O O is predicted to be 0.02 A longer than experiment. The heat of formation for F O O is computed to be 2.9 kcal/mol with an uncertainty of 2 3 kcal/mol. Preliminary results for FOOF (obtained with smaller basis set) iniicate that the approach yields a somewhat too long F O bond distance (1.64 A compared to 1.58 A experimentally). 0

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