Kinetic and thermodynamic aspects of excimer formation in 2,4-diphenylpentanes as polystyrene models

Precursor and interstitial Cajal cells in the human embryo liver

Interstitial Cajal Cells (ICCs) were only proven in human adult hepatic tissue. The immune phenotypes of various cell types in the human embryonic liver (HEL) are scarcely described. It was hypothesized that in HEL ICCs are present and distinctive to the precursor/progenitor cells populations. It was aimed and performed a qualitative study of HEL by use of antibodies against CD117/c-kit, CD31, CD34, CD90, CD105, DOG1, Ki67, and adiponectin. Five human embryos of 23-29 mm were used. Blasts and hematopoietic cells were comprising the two major cell populations in late stage embryos. The general population of blasts in the HEL was CD34-/CD105, although scarce CD117/c-kit+ and CD90+ such cells were found. Hematopoietic precursors were Ki67+. Adiponectin-positive plasmalemmas were found mostly in blasts. Endothelia were CD31+/CD34+. Interstitial cells with moniliform prolongations were found; such cells were scarcely CD117/c-kit+ but consistently DOG1+. They were diagnosed as ICCs but based on the morphology of their prolongations they can be equally viewed as being telocytes (TCs). Further studies should better correlate the precursor cell-types and immune phenotypes during human liver organogenesis. Liver ICCs and/or TCs should be also investigated in the human fetal liver.

Diastereodifferentiation of Novel Naphthalene Dyads by Fluorescence Quenching and Excimer Formation

Four new bichromophoric naphthalene dyads in form of diastereomeric pairs are synthesized and photophysically characterized. For a closely related group of compounds (NAP-NAP, MNAP-NAP, MNAP-MNAP), systematic variation of the urea linker led to the observation of intramolecular fluorescence quenching for tertiary urea, but not for secondary urea. Chiral information contained in the dyads has an impact on the efficiency of this process. Furthermore, for the case of (R,R)-MNAP-MNAP, excimer formation in the pre-organized dyad was noted, while being absent in the corresponding (R,S) diastereomer. These differences in photophysical behavior are ascribed to the geometry of the linker and to the chiral information contained in the diastereomeric compounds. Other dyads, such as NPX-NPX, included naproxen as the chromophore. For these compounds strong excimer emission is obtained, however, only very small diastereodifferentiation is observed for the two investigated stereoisomers.