Pii: S0040-4020(00)00525-1
نویسندگان
چکیده
ÐPhotocleavage of proteins by a series of organic probe molecules is examined as a function of probe structure. For example, pyrenyl peptides Py-Gly-X (XTrp, Tyr, Phe, and His, and Py4(1-pyrenyl)butyroyl)) are prepared, and their protein binding/photocleavage properties have been examined. The binding constants with bovine serum albumin (BSA) are in the range of 10 to 10 and binding of the probes to the proteins is evident in absorption, ̄uorescence and circular dichroism experiments. While the ̄uorescence of Py-Gly-Tyr increases upon binding to BSA, quenching is observed with Py-Gly-Trp or Py-Gly-His. While hyperchromism is observed with Py-Gly-Trp/BSA, hypochromism is the norm for all the other probes with this protein. Binding of all the probes to BSA or lysozyme resulted in major changes in the circular dichroism spectra of the probes. Photoexcitation of the probe/protein complexes, in the presence of an electron acceptor, resulted in protein photocleavage. The phenylalanine and histidine analogs resulted in photocleavage of both BSA and lysozyme while the tyrosine and tryptophan analogs did not yield any fragmentation with either of the two proteins. The photocleavage sites are similar to those reported for Py-Phe. Flash photolysis studies of the probe/protein mixtures indicate that the initially produced pyrene cation radical is strongly quenched by the tyrosine and tryptophan residues and resulted in the corresponding amino acid radicals. Strong modulation of the photoreactivities of the probes by speci®c residues of the probe provide insight in learning how the photocleavage ef®ciencies of the probes can be improved in future studies. q 2000 Elsevier Science Ltd. All rights reserved.
منابع مشابه
Pii: S0040-4020(00)00678-5
The diazo group of a series of a-diazo carbonyl compounds can be reduced to the corresponding CH2 group by Bu3SnH under Cu(acac)2-catalytic or photochemical conditions. The mechanistic aspects of this reaction were investigated in some detail, and a possible reaction pathway was discussed. q 2000 Elsevier Science Ltd. All rights reserved.
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ÐKnoevenagel condensation between 3-nitro-2-pyridinecarbaldehyde and diethyl malonate catalyzed by titanium(IV) chloride gave diethyl 3-nitro-2-pyridylidenemalonate which was oxidized with peracetic acid to give corresponding 1-oxide. Reaction of the latter with diethylamine in the presence of primary and secondary alcohols resulted in the reduction of the nitro group and the oxidation of the v...
متن کاملPii: S0040-4020(00)00886-3
ÐTwo constrained analogs of the tripeptide hormone thyroliberin (TRH) have been synthesized. In both, the HisPro peptide bond of the hormone has been `locked' into a cis-conformation. In the ®rst analog, the constraint used was identical to the constraint used in an earlier trans-peptide bond analog that was a potent agonist for the TRH endocrine receptor TRH-R1. The second analog was built in ...
متن کاملPii: S0040-4020(97)00801-6
The synthesis of two classes of Philanthotoxin-343 analogs is described. Quantitative information on the antagonism of quisqualate-sensitive ionotropic glutamate receptors of insect muscle by these compounds is presented. © 1997 Elsevier Science Ltd.
متن کاملPii: S0040-4020(97)10223-x
The nickel-catalyzed intramolecular cycloaddition of dienes with unactivatable alkynes is found to proceed under mild conditions while the corresponding Diels-Alder cycloaddition of the same substrates either fails or occurs only under forcing conditions. The nickel-catalyzed cycloaddition is also shown to occur with retention of stereochemistry and is not significantly influenced by electronic...
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