The aim of the work was to compare glycation-related changes in thermal denaturation of collagen in naturally ageing and in vitro ribosylated tissues. Samples of cornea, meniscus and Achilles tendon from young adult and from ageing rabbits were compared. Moreover, in vitro glycated samples (ribose, 100 mg mL -1 , 14 days) were prepared for both age groups. Collagen in tissues was characterized in terms of thermal denaturation parameters obtained from differential scanning calorimetry. The level of pentosidine and other fluorescent advanced glycation end products (AGEs) in the papain-digested tissue samples was evaluated using spectrofluorimetry (k ex/em : 335/385 and 370/440 nm). In naturally ageing tissues, changes in properties of extracellular matrix collagen expressed in terms of parameters of thermal denaturation and fluorescent AGEs levels were tissue dependent and were related to differences in organization of matrix components. No signs of increased level of AGEs were found in the naturally ageing cornea, unlike in the tendon and meniscus. In vitro ribation proved by gains of fluorescent AGEs affected thermal stability of collagen in all tissues, both in young adult and in the ageing ones. The effects of ribation were considerably greater than the effects of natural ageing. The increase in denaturation temperature was similarly strong in all tissues and did not correlate with the increase in fluorescent AGEs. As a conclusion, parameters of collagen thermal denaturation are tissue and age dependent and an amount of fluorescent AGEs is not the only determinant of increasing thermal stability of glycated collagen.

Basic thermodynamic functions responsible for retention of new 1,2,4-triazole derivatives exhibiting varied antiepileptic activity on cholesterol-based stationary phase were determined. Evaluation of the Gibbs energy change, the change in enthalpy and the change in entropy was based on the van't Hoff relationship representing lnk versus 1/T. A detailed discussion of the van't Hoff equation, exploring the influence of the phase ratio on deviations from linearity in a van't Hoff plot is presented. We show chromatographic evidence to the question of how a varied mobile phase composition may cause different thermodynamic phase ratios. The analysis of data from a differential scanning calorimetry excluded any phase transitions of either the individual solutes or cholesterol stationary phase suspended in the mobile phase components within the studied temperature range.

Liquid chromatography coupled to spectrophotometric detection of new antiepileptic compounds, 1,2,4‐triazole‐3‐thione derivatives, on immobilized artificial membrane phosphatidylcholine is reported. The curves representing the relationship between ln k versus 1/T generated under isocratic conditions by the use of methanol and acetonitrile‐containing eluent systems have been constructed in order to determine the thermodynamic parameters: the enthalpies, entropies and the relative free energies. The hydrocarbon chains of analytes significantly influenced the membrane behavior of the whole molecules. Excellent correlations of the theoretical lipophilicity with the experimental thermodynamic descriptors, have confirmed contribution of the hydrophobic interactions in the retention process. However, presence of sulfur or oxygen as heteroatoms at R1 substituents in the 1,2,4‐triazole ring appears to be responsible for more pronounced selectivity of these compounds on the phosphatidylcholine stationary phase. Molecular dynamics simulations revealed the selective preferences of the phosphatidylcholine with respect to the compounds with either ether of sulfide moieties. Experimental and theoretical set‐ups resulted in corresponding outcomes.