Raman cross sections for excitation at wavelengths between 240 and 192 nm have been determined for resonance-enhanced ring modes of phenylalanine (Phe), tyrosine (Tyr), tyrosinate (Tyr"), and tryptophan (Trp) and for the breathing mode of S042" and the symmetric OH stretching mode of H20. The S042" and H20 bands, which are frequently used for relative intensity measurements, show strong preresonance enhancement at wavelengths below 220 nm, requiring large corrections to convert relative to absolute intensities. The aromatic amino acid intensity measurements were obtained with laser power levels in the linear regime and appear not to be influenced by saturation effects or photochemical transients. The 1210-cm"1 ring-C stretching mode of Phe and Tyr and the ring modes v12 (Phe, 1000 cm"1) or (Tyr, 850 cm'1) show strong enhancement in resonance with the allowed Bab transition and weak enhancement in resonance with the quasi-forbidden La transition. Their excitation profiles (EPs) peak on the red side of the La absorption band, consistent with destructive interference between La and Bab contributions to the /1-term Raman amplitude. The modes v8a, v8b (~1610, 1590 cm"1), and u9a (^-1180 cm"1), known to be responsible for the vibronic intensity of the La transition, are resonant with the La transition but also with the Ba b transition. Enhancement of v8b, which is antisymmetric in the molecular C2c symmetry, requires 5-term activity for the Ba b as well as the La states. The Ba b enhancement (192-nm excitation) of y8b, as well as v8a and v9a, increases in the order Phe < Tyr < phenolate « Tyr". This effect is suggested to arise from the substituent electronic perturbation, which leads to a Ba origin shift along v8a and i/9a and vibronic mixing between Ba and Bb via v8b. In the La region the EPs of v8a, vsb, and v9a are skewed to the blue side of the La absorption band, for Tyr more than Phe, suggesting constructive La-Bab interference for the 5 Raman terms. The Phe v8a and v8b overtones and combination bands are more strongly enhanced in resonance with Ba b than are the fundamentals; the 2v8a/v8a intensity ratio reaches a value of 2.1 at 192 nm. This effect is attributed to force constant changes in the allowed excited states. The 2v8a cross section is much lower for Tyr but increases again for Tyr", although the fundamental band is now much stronger. Evidently the Ba force constant change is diminished by the OH substituent, while the increased origin shift for O" increases the overtone intensity again. The Tyr 2u8b cross sections are about half those of Phe and the 2v8b/v8b ratio, ~0.15, is suggested to reflect the relative magnitude of C and 5 vibronic terms. Several Trp modes give EPs which track the strong 220-nm absorption band, attributed to Bb. These modes have significant fiveand six-membered ring involvement, implying delocalized character for the transition. The benzene-like v8a and v8b modes are enhanced in the short-wavelength absorption band (~1 95 nm), attributed to Ba. The »8a mode is also weakly resona...

Herpes simplex virus infections are the cause of significant morbidity, and currently used therapeutics are largely based on modified nucleoside analogs that inhibit viral DNA polymerase function. To target this disease in a new way, we have identified and optimized selective thiazolylphenyl-containing inhibitors of the herpes simplex virus (HSV) helicase-primase enzyme. The most potent compounds inhibited the helicase, the primase and the DNA-dependent ATPase activities of the enzyme with IC50 (50% inhibitory concentration) values less than 100 nM. Inhibition of the enzymatic activities was through stabilization of the interaction between the helicase-primase and DNA substrates, preventing the progression through helicase or primase catalytic cycles. Helicase-primase inhibitors also prevented viral replication as demonstrated in viral growth assays. One compound, BILS 179 BS, displayed an EC50 (effective concentration inhibiting viral growth by 50%) of 27 nM against viral growth with a selectivity index greater than 2,000. Antiviral activity was also demonstrated for multiple strains of HSV, including strains resistant to nucleoside-based therapies. Most importantly, BILS 179 BS was orally active against HSV infections in murine models of HSV-1 and HSV-2 disease and more effective than acyclovir when the treatment frequency per day was reduced or when initiation of treatment was delayed up to 65 hours after infection. These studies validate the use of helicase-primase inhibitors for the treatment of acute herpesvirus infections and provide new lead compounds for optimization and design of superior anti-HSV agents.

The binding site on the lymphocyte function-associated antigen-1 (LFA-1) of a class of hydantoin-based antagonists of leukocyte cell adhesion has been identified. This site resides in the inserted-domain (I-domain) of the CD11a chain at a location that is distal to residues known to be required for interactions with the intercellular adhesion molecules. This finding supports the hypothesis that the molecules are antagonizing cell adhesion via an allosteric modification of LFA-1. The binding site was identified using an integrated immunochemical, chemical, and molecular modeling approach. Antibodies that map to epitopes on the I-domain were blocked from binding to the purified protein by the hydantoins, indicating that the hydantoin-binding site resides on the I-domain. Photoaffinity labeling of the I-domain followed by LC/MS and LC/MS/MS analysis of the enzymatic digest identified proline 281 as the primary amino acid residue covalently attached to the photoprobe. Distance constraints derived from this study coupled with known SAR considerations allowed for the construction of a molecular model of the I-domain/inhibitor complex. The atomic details of the protein/antagonist interaction were accurately predicted by this model, as subsequently confirmed by the X-ray crystal structure of the complex.

A novel inhibitor of p38 mitogen-activated protein kinase (p38), CMPD1, identified by high-throughput screening, is characterized herein. Unlike the p38 inhibitors described previously, this inhibitor is substrate selective and noncompetitive with ATP. In steady-state kinetics experiments, CMPD1 was observed to prevent the p38alpha-dependent phosphorylation (K(i)(app) = 330 nM) of the splice variant of mitogen-activated protein kinase-activated protein kinase 2 (MK2a) that contains a docking domain for p38alpha and p38beta, but it did not prevent the phosphorylation of ATF-2 (K(i)(app) > 20 microM). In addition to kinetic studies, isothermal titration calorimetry and surface plasmon resonance experiments were performed to elucidate the mechanism of inhibition. While isothermal titration calorimetry analysis indicated that CMPD1 binds to p38alpha, CMPD1 was not observed to compete with ATP for p38alpha, nor was it able to interrupt the binding of p38alpha to MK2a observed by surface plasmon resonance. Therefore, deuterium exchange mass spectrometry (DXMS) was employed to study the p38alpha.CMPD1 inhibitory complex, to provide new insight into the mechanism of substrate selective inhibition. The DXMS data obtained for the p38alpha.CMPD1 complex were compared to the data obtained for the p38alpha.MK2a complex and a p38alpha.active site binding inhibitor complex. Alterations in the DXMS behavior of both p38alpha and MK2a were observed upon complex formation, including but not limited to the interaction between the carboxy-terminal docking domain of MK2a and its binding groove on p38alpha. Alterations in the D(2)O exchange of p38alpha produced by CMPD1 suggest that the substrate selective inhibitor binds in the vicinity of the active site of p38alpha, resulting in perturbations to regions containing nucleotide binding pocket residues, docking groove residues (E160 and D161), and a Mg(2+) ion cofactor binding residue (D168). Although the exact mechanism of substrate selective inhibition by this novel inhibitor has not yet been disclosed, the results suggest that CMPD1 binding in the active site region of p38alpha induces perturbations that may result in the suboptimal positioning of substrates and cofactors in the transition state, resulting in selective inhibition of p38alpha activity.

6. Raman excitation profiles of the drug in solution and bound to calf thymus DNA were obtained. There were no changes in the Raman frequencies upon interaction with nucleic acids, only a decrease in intensity.(CHE-8510614) for partial support of this work.