In vivo fluorescence imaging using two excitation and/or emission wavelengths for image contrast enhancement

Steady-state fluorescence imaging can be used in conjunction with selective exogenous or endogenous fluorescent compounds for the diagnosis of skin lesions, for example cancer. Depending on the excitation and emission properties of the fluorescent compound used, various excitation and/or emission wavelengths can be chosen in order to allow fluorescence imaging. Unwanted background signals such as autofluorescence and scattering can decrease the image quality and, hence, the diagnosis potential of this imaging method. We have used an inexpensive dual excitation and/or emission wavelength approach in order to suppress the unwanted background signal and allow contrast enhanced fluorescence imaging. One excitation and/or emission wavelength is at the corresponding maximum of the fluorescent compound, while the second is at a nearby excitation/emission minimum. The first image contains the emission from the fluorescent compound used combined with the signal from the unwanted background. The second image provides an image of just the unwanted background signal. The difference of both images taken, thus gives a contrast enhanced image of the skin lesion. The method relies on the assumption that the background signal does not change significantly due to the small changes in wavelength for excitation or emission. Image ratio methods have already been applied towards diagnosis of basal cell carcinomas after administration of aminolevulinic acid-induced protoporphyin IX. In this study, we describe in vivo measurements in mice where the second image, usually the background signal only, contains new unwanted image data. This simple method can successfully resolve the desired image, thus demonstrating the versatility of the image processing procedure.     

Equivariant normal form for nondegenerate singular orbits of integrable Hamiltonian systems

We consider an integrable Hamiltonian system with n degrees of freedom whose first integrals are invariant under the symplectic action of a compact Lie group G. We prove that the singular Lagrangian foliation associated to this Hamiltonian system is symplectically equivalent, in a G-equivariant way, to the linearized foliation in a neighborhood of a compact singular nondegenerate orbit. We also show that the nondegeneracy condition is not equivalent to the nonresonance condition for smooth systems.     

Nouveaux exemples de radicaux libres stables de dérivés hétérocycliques de sucres. Communication préliminaire

Some more examples of stable free radicals of carbohydrate heterocyclic derivatives 2-Glycosyl-4,4,5,5-tetramethylimidazoline- 3-oxide-1-oxyls and 2-glycosyl-4,4,5,5-tetramethylimidazoline 1-oxyls have been prepared in nine carbohydrate series, which proves the generality of the method. The hyperfine coupling constant between the free electron and the α-proton of the glycosyl group is never very large (0-2.3 G) but a correlation between its value and the structure of the aglycone has been noted. Free radicals of that type, stable in aqueous solutions, are potentially interesting for biological studies.     

Six new photolabile linkers for solid phase synthesis. 2. Coupling of various building blocks and photolytic cleavage

Photolabile linkers are very useful in the generation of combinatorial libraries as they offer compound cleavage under mild conditions directly into a solvent suitable for biological testing. Six new photolabile linkers have been developed which allow coupling of building blocks with a carboxy, amino, hydroxy and sulfonyl group. Photolytic cleavage of these building blocks will give libraries with carboxy, amido, methylamido, amino, ureido, hydroxy, aminocarbonyloxy and aminosulfonyl terminal groups. Coupling conditions for these reactions were elucidated and the photolytic cleavage reaction was studied.     

Studies on chymotrypsin-like catalysis by synthetic peptides

The synthetic peptide Chymohelizyme-1 (CHZ-1) exhibits esterase activity against carbobenzoxytyrosinep-nitrophenyl ester (ZTONP), carbobenzoxyalaninep-nitrophenyl ester (ZAONP), andt-butyloxycarbonyltyrosinep-nitrophenyl ester (BocTONP). However, earlier reports of catalytic activity against less labile esters and amides have proven to be incorrect. The major reason for the errors appears to have been the omission of certain controls in the previous work. Although the catalytic triad does not appear to be functioning as designed, the catalytic activity of CHZ-1 does depend on the integrity of its primary structure. The pH dependence of hydrolysis of ZTONP points to general-base catalysis, whereas a preference for hydrophobic substrates suggest that the structure of CHZ-1 is performing some other role in assisting catalysis.