The synthesis and characterization of aromatic−aliphatic polyesters with tailored degree of branching (DB), i.e. hyperbranched (hb), gradually branched, and linear polymers, are described. The dilute solution properties of polymers resulting from two different synthetic approaches are compared. The ABB*/AB2 approach leads to homopolymers with different DB based on the same AB2 monomer, 4,4-bis(4′-hydroxyphenyl)pentanoic acid, employing the protection of one phenolic group (B*) in the AB2 monomer followed by copolymerization with AB2 monomer at different molar ratios. Because of their identical chemical origin, well-tunable DB, comparable molar masses, an absence of aggregation in common solvents, and high refractive index increments, they are suitable as model systems in branching characterization. Their solution properties are compared to those of polymers obtained by the AB/AB2 approach. In order to study the influence of the end-groups on thermal and solution polymer properties, all terminal OH groups were modified with tert-butyldimethylsilyl chloride (SY-Cl). A different dependence of the thermal properties on branching was found for OH- and SY-terminated samples produced by the ABB*/AB2 approach. While the difference in the T g values between linear and hb structures was found to be 16 °C for SY-terminated samples, nearly identical values were obtained for OH-terminated linear and hb polyesters due to strong effect of hydrogen bond formation.

The retention behavior of aromatic polyesters possessing different degrees of branching was studied in gradient liquid adsorption chromatography (gradient chromatography), liquid adsorption chromatography (LAC), and liquid chromatography at the critical conditions (LCCC). The chromatographic experiments revealed that retention of linear and branched polyesters is influenced by the degree of branching as well as the molar mass of the polymer samples in all enthalpy-dominated chromatographic modes such as LAC, LCCC, and gradient chromatography. At critical conditions of the linear polymer, the corresponding branched structures elute in the adsorption mode, indicating a stronger adsorptive interaction between the stationary phase and the branched polymer molecule. In gradient chromatography, polymer samples with higher degrees of branching are retarded longer on the stationary phase. A clear dependence between the degree of branching and the elution volume was found in both chromatographic modes, which clearly demonstrates a pronounced effect of topology on retention behavior. The results suggest the use of gradient chromatography as a first separation step for a two-dimensional characterization method of branched polymers in order to separate by both degree of branching and molar mass.

Remarkably elevated levels of phospholipase A 2 (PLA 2 ) are measurable in human blood samples in cases of acute pancreatitis. The source of the enzyme was first thought to be exclusively the pancreas, but now it is generally accepted that two isoenzymes − the pancreatic PLA 2 , group I, and the extrapancreatic PLA 2 , group II − contribute to the raised activity. In contrast to the group II-PLA 2 , the pancreatic PLA 2 is heat-resistant for 1 hour at 60 °C. The catalytically inactive proenzyme of the pancreatic PLA 2 can be activated by trypsin. The aim of our study was to evaluate the diagnostic value of PLA 2 isoenzyme activity measurements to identify patients with severe complications in acute pancreatitis. Blood samples from patients suffering from acute pancreatitis were analyzed for catalytically active pancreatic PLA 2 on day 1 and 2 of hospitalization with a modified radiometric Escherichia coli-based PLA 2 assay. In 10 of 41 patients clearly elevated values of catalytically active, heat-resistant pancreatic PLA 2 (7.2 to 81.2 U/l) were observed. This group of patients was characterized by severe complications (necrotizing pancreatitis, shock, sepsis, respiratory problems) of which two patients subsequently died. Patients with low or undetectable activity (<7 U/l) of pancreatic PLA 2 recovered rapidly. According to these results the presence of catalytically active pancreatic PLA 2 in serum is associated with severe complications of acute pancreatitis. In contrast to total serum-PLA 2 , the catalytic concentration of pancreatic PLA 2 can serve as a prognostic marker in acute pancreatitis. Clin Chem Lab Med 2002; 40(3):293-297

The vertical gradient of skin distensibility was described for the first time. This appears a prerequisite to resist the hydrostatic pressure and influences of gravity. The findings may have important implications in leg ulcer and gravitational syndrome.