Irisin immunohistochemistry in gastrointestinal system cancers

Cancer is the leading cause of morbidity and mortality worldwide. Some studies have shown that high heat kills cancer cells. Irisin is a protein involved in heat production by converting white into brown adipose tissue, but there is no information about how its expression changes in cancerous tissues. We used irisin antibody immunohistochemistry to investigate changes in irisin expression in gastrointestinal cancers compared to normal tissues. Irisin was found in human brain neuroglial cells, esophageal epithelial cells, esophageal epidermoid carcinoma, esophageal adenocarcinoma and neuroendocrine esophageal carcinoma, gastric glands, gastric adenosquamous carcinoma, gastric neuroendocrine carcinoma, gastric signet ring cell carcinoma, neutrophils in vascular tissues, intestinal glands of colon, colon adenocarcinoma, mucinous colon adenocarcinoma, hepatocytes, hepatocellular carcinoma, islets of Langerhans, exocrine pancreas, acinar cells and interlobular and interlobular ducts of normal pancreas, pancreatic ductal adenocarcinoma, and intra- and interlobular ducts of cancerous pancreatic tissue. Histoscores (area × intensity) indicated that irisin was increased significantly in gastrointestinal cancer tissues, except liver cancers. Our findings suggest that the relation of irisin to cancer warrants further investigation.     

Calorimetric studies of p-nitrophenol binding to α- and β-cyclodextrin

The thermodynamics of the binding of p-nitrophenol to both α- and β-cyclodextrin has been investigated as a function of pH and solvent composition using the technique of flow microcalorimetry. A preferential binding of the anionic form of the ligand is found for both cyclodextrins. It is postulated that the additional affinity for p-nitrophenolate is due to a dispersion interaction between the cyclodextrin cavity and the delocalized charge of the ligand. Studies of the binding of p-nitrophenol analogs and of the binding of p-nitrophenol as a function of ionic strength and DMSO cosolvent composition are consistent with this theory.     

Pressure dependence of fluorescence quenching reactions in proteins

The effect of hydrostatic pressure (0-2.6 kbar) on the acrylamide quenching of the fluorescence of indole derivatives and several single-tryptophan-containing proteins has been studied using phase fluorometry at 25 degrees C. For the model system, N-acetyl-L-tryptophanamide in water, there is essentially no pressure dependence of the quenching rate constant, kappa q. For the internal Trp residue of ribonuclease T1 and cod parvalbumin, there also is essentially no pressure dependence of the apparent kappa q at low pressure. Thus, the activation volume, delta V not equal to, for these quenching processes is approximately zero. Such small delta V not equal to values are expected for diffusion-limited reactions in water at this temperature. The low, apparent delta V not equal to values for the globular proteins characterize these quenching processes as involving very small amplitude fluctuations in the protein structures. Only for the poised tetramer in equilibrium monomer equilibrium of melittin were we able to observe a significant effect of pressure on kappa q and this is due to the pressure-induced shift in the equilibrium position.     

Fluorescence quenching of Trp-314 of liver alcohol dehydrogenase by oxygen

The quenching of the fluorescence of liver alcohol dehydrogenase (LADH) by molecular oxygen has been studied by both fluorescence lifetime and intensity measurements. This was done in the presence of 1 M acrylamide which selectively quenches the fluorescence of the surface tryptophan residue, Trp-15, thus allowing us to focus on the quenching of the deeply buried tryptophan, Trp-314, by molecular oxygen. Such studies yielded a Stern-Volmer plot of F0/F with a greater slope than the corresponding tau o/tau plot. This indicates that both dynamic and static quenching of Trp-314 occurs. The temperature dependence of the dynamic quenching of LADH by oxygen was also studied at three temperatures, from which we determined the activation enthalpy for the quenching of Trp-314 to be about 10 kcal/mol. The oxygen quenching of a ternary complex of LADH, NAD+ and trifluoroethanol was also studied. The rate constant for dynamic quenching of Trp-314 by oxygen was found to be approximately the same in the ternary complex as that in the unliganded enzyme.     

The application of flow microcalorimetry to the study of enzyme kinetics

The use of flow microcalorimetry to measure velocities for enzyme-catalyzed reactions is described. Studies are presented involving the enzymes chymotrypsin, trypsin, and ribonuclease A. In determining the Michaelis-Menten parameters, V_m and K_m, for these systems complications arise due to substrate depletion and product inhibition. By employing an integrated Michaelis-Menten equation, V_m and K_m can be determined.     

Fluorescence quenching studies with proteins

A review is presented on the use of the technique of solute fluorescence quenching to study the structure and dynamics of proteins. A number of factors are discussed that must be considered in analyzing such data. Among these factors are the efficiency of the quenching process, the relative importance of static quenching, the heterogeneity of the emission, and the tendency of the quencher to interact with the protein.