Electronic energy harvesting multi BODIPY-zinc porphyrin dyads accommodating fullerene as photosynthetic composite of antenna-reaction center.

Efficient electronic energy transfer (EET) in the newly synthesized dyads comprised of zinc porphyrin covalently linked to one, two or four numbers of boron dipyrrin (BDP) entities is investigated. Both steady-state and time-resolved emission as well as transient absorption studies revealed occurrence of efficient singlet-singlet energy transfer from BDP to zinc porphyrin with the time scale ranging between 28 and 48 ps. A decrease in time constants for energy transfer with increasing the number of BDP units is observed revealing better antenna effect of dyads bearing higher number of boron dipyrrin entities. Further, supramolecular triads to mimic the 'antenna-reaction center' functionality of photosynthetic reaction center have been successfully constructed by coordinating fulleropyrrolidine appended with an imidazole ligand to the zinc porphyrin. The structural integrity of the supramolecular triads was arrived by optical, computational and electrochemical studies. Free energy calculations revealed possibility of photoinduced electron transfer from singlet excited zinc porphyrin to fullerene, and the preliminary transient absorption studies involving pump-probe technique are supportive of occurrence of electron transfer from (1)ZnP* to fullerene in the supramolecular triads.

Derivatives of 3-alkyl-N-hydroxysuccinimide: probing the effect of structure on bioactivity toward human leukocyte elastase.

A structure-activity relationship study was conducted in order to probe the nature of the interaction between some 3-alkyl-N-hydroxysuccinimide derivatives and human leukocyte elastase. The structural features in substituent X (structure I) that lead to the manifestation and optimization of inhibitory activity have been examined. The data suggest that the presence of an alkyl or aryl(sulfonyloxy) group in the active compounds may serve a triple purpose, namely, it functions as a good leaving group as dictated by the established mechanism of action of this class of compounds, secondly, it may enhance binding by assuming a favorable spatial orientation and, thirdly, it may increase the chemical reactivity of the carbonyl carbon in the bioactive compounds.

Inactivation of leukocyte elastase by aryl azolides and sulfonate salts. Structure-activity relationship studies.

The inhibitory activity of a series of aryl azolides and sulfonate salts toward human leukocyte elastase is reported. Several of the compounds were found to be potent inhibitors of the enzyme. Active compounds were obtained only when the specificity group and the reactive moiety were separated by a two-carbon chain. The introduction of hydrophobic groups enhanced the inhibitory activity of these compounds, with the exception of the sulfonate salts. The nature of the leaving group had a profound effect on inhibitory activity, with compounds 23 and 26 being the most active (kobsd/[I] = 11,722 and 13,500 M-1 s-1, respectively).

Sulfonate salts of amino acids: novel inhibitors of the serine proteinases.

A series of amino acid-derived sulfonate salts have been synthesized. They were found to inactivate efficiently and selectively human leukocyte elastase. The sulfonate salts of the methyl esters of L-norleucine, L-norvaline and L-valine were the most potent. The enzyme is inactivated irreversibly with concomitant release of bisulfite ion. The results demonstrate for the first time that ionic compounds can indeed function as novel inhibitors for the serine proteinases.