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These notes, based on work with Herbi Dreiner and Howie Haber, discuss how to do practical calculations of cross sections and decay rates using twocomponent fermion notation, as appropriate for supersymmetry and other beyond-the-Standard-Model theories. Included are a list of two-component fermion Feynman rules for the Minimal Supersymmetric Standard Model, and some example calculations. [ABSTRACT FROM AUTHOR]

Only four intrinsic protein chromophores absorb light significantly in the near-UV region of the spectrum (340-255 nm): the side chains of Trp, Tyr, Phe, and cystine (note: cysteine residues make no significant contribution). The absorption spectra are shown in Fig. 1. Although several amino acid side chains (notably Tyr, Trp, Phe, His, and Met) absorb light strongly in the far-UV region (below 250 nm), the most important contributor here is the peptide bond (amide chromophore), with n ?π * and π ? π * transitions at approx 220 nm and approx 190 nm, respectively. The contribution of any individual chromophore to the total absorbance of the protein will depend, to some extent at least, upon its environment. The experimentally measured parameter, the absorbance A is related to the molar extinction coefficient, εM (M-1cm-1), the path length l (cm), and the protein concentration C (M) by the Beer-Lambert law A = εM.C.l. [ABSTRACT FROM AUTHOR]

The use of substituted cyclopropanes as conformationally constrained peptidomimetics has received considerable attention recently (1-6). The efforts from our laboratory in this area have focused on the use 1,2,3-trisubstituted cyclopropanes as novel isosteric replacements in several biological systems (7-10). A common theme of this program has been the use of trans-substituted cyclopropanes to enforce extended or "β-strand" secondary structure while orienting the amino acid side chain in a predictable conformation (11). In an effort to explore further the utility of this novel isostere, modeling and calculations suggested that a cis-substituted cyclopropane dipeptide subunit could stabilize a turn structure. The focus of this chapter is to describe the preparation of a novel cyclopropane-containing cis-substituted (-Glyψ[CHOH-cp-CONH]-) subunit, which replaces Gly2-Gly3 subunit of the Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu) framework shown in Fig. 1. [ABSTRACT FROM AUTHOR]

The use of cyclopropanes as a conformationally restricted subunits in biological systems has been the subject of intense study by our group and others (1-10). Our recent efforts have focused on the use of 1, 2, 3-trisubstituted cyclopropanes as novel [-NH-Cα-] or [-CO-Cα-] bond replacements in pseudopeptides to restrict both side-chain orientation and enforce backbone secondary structures. To test these assumptions, the cyclopropane containing analog 1 (Fig. 1) was modeled after the potent HIV protease inhibitor 2, which together with a series of related derivatives was developed at Abbott Laboratories (11). This pseudopeptide contains a symmetrical diamino diol motif 8 (Fig. 2) flanked by Cbz-protected valine residues and is known to bind in a β-strand fashion at the enzyme-active site (12). Our analog 1 was designed to restrict the orientation of the valine residues and to mimic this "extended" backbone conformation. Comparison of enzyme inhibition constants for both compound 1 and the parent inhibitor 2 will then elucidate the efficacy of the cyclopropane as a conformationally restrictive subunit. [ABSTRACT FROM AUTHOR]