Synthesis, activity and toxicity of novel macrocyclic ligands against HIV-1 in Jurkat and CEM-SS cell lines.

We have developed versatile synthetic routes that afford metal-free macrocycles containing different functionalities in their framework. Novel oxaziridine and amide containing macrocycles were synthesized, and the metal complexes of the latter were also prepared. A series of theophilline and thymidine side-arm containing podands as well as macrocycles were obtained employing the same methodology.

Hydrogen bond interactions of G proteins with the guanine ring moiety of guanine nucleotides.

We have utilized Raman difference spectroscopy to investigate hydrogen bonding interactions of the guanine moiety in guanine nucleotides with the binding site of two G proteins, EF-Tu (elongation factor Tu from Escherichia coli) and the c-Harvey ras protein, p21 (the gene product of the human c-H-ras proto-oncogene). Raman spectra of proteins complexed with GDP (guanosine 5' diphosphate), IDP (inosine 5' diphosphate), 6-thio-GDP, and 6-18O-GDP were measured, and the various difference spectra were determined. These were compared to the difference spectra obtained in solution, revealing vibrational features of the nucleotide that are altered upon binding.

An isotope edited classical Raman difference spectroscopic study of the interactions of guanine nucleotides with elongation factor Tu and H-ras p21.

We have measured the Raman spectrum of GDP bound to the elongation factor protein, EF-Tu, and the c-Harvey-ras protein, p21, two proteins of the guanine nucleotide binding family. In order to separate the Raman spectrum of the nucleotide from the much more intense protein spectrum, we investigate the feasibility of "tagging" the normal modes of the nucleotide by isotopic substitution, here by incoporating deuterium-labeled guanine at the C8 position into the active site. A difference spectrum between the labeled and unlabeled protein-nucleotide complex shows the changes in the Raman spectrum of the bound nucleotide that arise from the isotopic exchange.

Mechanism of isomerization of rhodopsin studied by use of 11-cis-locked rhodopsin analogues excited with a picosecond laser pulse.

Primary photochemical behaviors of cattle rhodopsin analogues (Rh5 and Rh7) having cyclopenta- and cycloheptatrienylidene 11-cis-locked retinals (Ret5 and Ret7, respectively) were studied by excitation with a picosecond laser pulse (wavelength 532 nm; duration 21 ps). Picosecond absorption and fluorescence measurements of Rh5 showed formation of only a long-lived excited singlet state (tau l/e = 85 ps). The excited state of the retinal analogue having a five-membered ring was stabilized in protein (Rh5) more than in solvent (protonated Schiff base of Ret5; PSB5).

Fourier-transform infrared difference spectroscopy of rhodopsin and its photoproducts at low temperature.

Fourier-transform infrared difference spectroscopy has been used to detect the vibrational modes in the chromophore and protein that change in position or intensity between rhodopsin and the photoproducts formed at low temperature (70 K), bathorhodopsin and isorhodopsin. A method has been developed to obtain infrared difference spectra between rhodopsin and bathorhodopsin, bathorhodopsin and isorhodopsin, and rhodopsin and isorhodopsin. To aid in the identification of the vibrational modes, we performed experiments on deuterated and hydrated films of native rod outer segments and rod outer segments regenerated with either retinal containing 13C at carbon 15 or 15-deuterioretinal.