Destillation

Ohne Zusammenfassung     

Phycobiliproteins encapsulated in sol-gel glass

Light transducing phycobiliproteins are encapsulated in optically transparent sol-gel matrices. Absorption and fluorescence spectroscopies are used to characterize the effect of the sol-gel encapsulation on the conformation and aggregation states of the three major phycobiliproteins present in phycobilisomes: phycoerythrin, phycocyanin, and allophycocyanin. It is found that the effects of sol-gel entrapment on the spectroscopic properties are significantly different for the three phycobiliproteins. The results indicate that phycoerythrin undergoes only minor change in its native structure when entrapped in sol-gel. However, significant changes in conformation and aggregation state occur when phycocyanin and allophycocyanin are entrapped in sol-gel matrices. A thin film of sol-gel encapsulated phycoerythrin is also coated on an optical fiber surface and strong fluorescence from the evanescent wave excitation is detected. The potential applications of sol-gel encapsulated phycobiliproteins in biosensors are discussed.     

The relative basicity of sulfur containing esters

The relative gas phase proton affinities for an amide, ester, and thiolester have been established as CH₃CONHCH₃ > CH₃COSCH₃ > CH₃COOCH₃ using ion cyclotron resonance techniques. A dithioester is more basic than the thiolester: CH₃CSSCH₃ > CH₃COSCH₃. d-Orbitals are unimportant in the electronic structure of thiolesters.