Di-, tri- and tetra-5'-O-phosphorothioadenosyl substituted polyols as inhibitors of Fhit: Importance of the α-β bridging oxygen and β phosphorus replacement

Background  

The human FHIT gene is inactivated early in the development of many human cancers and loss of Fhit in mouse predisposes to cancer while reintroduction of FHIT suppresses tumor formation via induction of apoptosis. Fhit protein, a diadenosine polyphosphate hydrolase, does not require hydrolase activity to function in tumor suppression and may signal for apoptosis as an enzyme-substrate complex. Thus, high affinity nonhydrolyzable substrate analogs may either promote or antagonize Fhit function, depending on their features, in Fhit + cells. Previously synthesized analogs with phosphorothioadenosyl substitutions and "supercharged" branches do not bind better than natural substrates and thus have limited potential as cellular probes.     

De novo synthesis of glycosaminoglycans by equine multipotent mesenchymal stromal cells in vitro – Studied by stable isotopic labeling and matrix-assisted laser desorption ionization mass spectrometry

Glycosaminoglycans (GAGs) play an important role in extracellular matrix (ECM) homeostasis and are crucial for maintaining the specific biomechanical and functional properties of musculoskeletal tissues. Aiming at regenerating these tissues, multipotent mesenchymal stromal cells (MSCs) are frequently used, their targeted differentiation and ECM synthesis being a part of their complex mechanism of action. To achieve a better understanding of these processes and to improve the targeted use of the cells for the development of regenerative therapies, reliable quantification of GAGs synthesized by MSCs represents an important step. The aim of this study was to develop a novel technique to specifically assess the de novo synthesis of GAGs, particularly chondroitin sulfate (CS), by MSCs.

Adipose tissue-derived equine MSCs were cultured in vitro for 2, 7, 14, and partially 28 d. Harvested cell populations were enzymatically digested with chondroitinase ABC from Proteus vulgaris and afterwards subjected to CS analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

The herein chosen detection method of MALDI-TOF MS combined with enzymatic digestion represents a reliable technique to monitor the culture time-dependent GAG biosynthesis of MSCs cultured in vitro. Furthermore, the addition of ¹³C-labeled glucose as cell culture medium supplement is a useful approach to obtain information regarding cellular GAG and in particular CS synthesis.     

N‐methylpicolinium derivatives as the coinitiators in photoinitiating systems for vinyl monomers polymerization

Five N‐methylpicolinium derivatives were investigated to test their abilities to function as second coinitiators in free radical photopolymerization initiated by N,N′‐diethylcarbocyanine—n‐butyltriphenylborate photoredox pair ( P19B2 ). As it is shown by the kinetic data, an addition of picolinium derivatives into P19B2 photoinitiating system visibly increases the efficiency of photoinitiation. The results suggest that the rates of photoinitiation depend on the rate of the picolyl radicals formation. The redox potentials of tested N‐methylpicolinium derivatives were measured and the calculation of free energy change for the possible electron transfer reactions between all components of the system (both stable and transient individuals) was performed. The results suggest that cyanine dyes are able to start a specific chain of an electron transfer reactions involving different coinitiators (borate salt and N‐alkylpicolinium derivatives), giving as a result one photon—two‐radicals photochemical response. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 576–588, 2009     

Real-time tracking of phytochrome's orientational changes during Pr photoisomerization

Photoisomerization of a protein bound chromophore is the basis of the light sensing and signaling responses of many photoreceptors. Z-to-E photoisomerization of the Pr Cph1Δ2 phytochrome has been investigated by polarization resolved femtosecond visible pump-infrared probe spectroscopy, which yields structural information on the Pr excited (Pr*), Pr ground, and lumi-R product states. By exhaustive search analysis, two photoreaction time constants of (4.7 ± 1.4) and (30 ± 5) ps were found. Ring D orientational change in the electronic excited state to the transition state (90° twist) has been followed in real-time. Rotation of ring D takes place in the electronically excited state with a time constant of 30 ± 5 ps. The photoisomerization is best explained by a single rotation around C(15)═C(16) methine bridge in the Pr* state and a diffusive interaction with its protein surrounding.