Time-Resolved Studies of the Excited-State Dynamics of meso-Tetra(hydroxylphenyl)chlorin in Solution

Meso-tetra(hydroxyphenyl)chlorin (m-THPC) is a new photosensitizer developed for potential use in photodynamic therapy (PDT) for cancer treatment. In PDT, the accepted mechanism of tumor destruction involves the formation of excited singlet oxygen via intermolecular energy transfer from the excited triplet-state dye to the ground triplet-state oxygen. Femtosecond transient absorption measurements are reported here for the excited singlet state dynamics of m-THPC in solution. The observed early time kinetics were best fit using a triple exponential function with time constants of 350 fs, 80 ps and > or = 3.3 ns. The fastest decay (350 fs) was attributed to either internal conversion from S2 to S1 or vibrational relaxation in S2. Multichannel time-resolved absorption and emission spectroscopies were also used to characterize the excited singlet and triplet states of the dye on nanosecond to microsecond time scales at varying concentrations of oxygen. The nanosecond time-resolved absorption data were fit with a double exponential with time constants of 14 ns and 250 ns in ambient air, corresponding to lifetimes of the S1 and T1 states, respectively. The decay of the T1 state varied linearly with oxygen concentration, from which the intrinsic decay rate constant, ki, of 1.5 x 10(6) s-1 and the biomolecular collisional quenching constant, kc, of 1.7 x 10(9) M-1 s-1 were determined. The lifetime of the S1 state of 10 ns was confirmed by fluorescence measurements. It was found to be independent of oxygen concentration and longer than lifetimes of other photosensitizers.     

Separation of 44Sc from 44Ti in the Context of A Generator System for Radiopharmaceutical Purposes with the Example of [44Sc]Sc-PSMA-617 and [44Sc]Sc-PSMA-I&T Synthesis

Today, ⁴⁴Sc is an attractive radionuclide for molecular imaging with PET. In this work, we evaluated a ⁴⁴Ti/⁴⁴Sc radionuclide generator based on TEVA resin as a source of ⁴⁴Sc. The generator prototype (5 MBq) exhibits high ⁴⁴Ti retention and stable yield of ⁴⁴Sc (91 ± 6 %) in 1 mL of eluate (20 bed volumes, eluent—0.1 M oxalic acid/0.2 M HCl) during one year of monitoring (more than 120 elutions). The breakthrough of ⁴⁴Ti did not exceed 1.5 × 10⁻⁵% (average value was 6.5 × 10⁻⁶%). Post-processing of the eluate for further use in radiopharmaceutical synthesis was proposed. The post-processing procedure using a combination of Presep^® PolyChelate and TK221 resins made it possible to obtain ⁴⁴Sc-radioconjugates with high labeling yield (≥95%) while using small precursor amounts (5 nmol). The proposed method takes no more than 15 min and provides ≥90% yield relative to the ⁴⁴Sc activity eluted from the generator. The labeling efficiency was demonstrated on the example of [⁴⁴Sc]Sc-PSMA-617 and [⁴⁴Sc]Sc-PSMA-I&T synthesis. Some superiority of PSMA-I&T over PSMA-617 in terms of ⁴⁴Sc labeling efficiency was demonstrated (likely due to presence of DOTAGA chelator in the precursor structure). It was also shown that microwave heating of the reaction mixture considerably shortened the reaction time and improved radiolabeling yield and reproducibility of [⁴⁴Sc]Sc-PSMA-617 and [⁴⁴Sc]Sc-PSMA-I&T synthesis.     

Phosphorylation of Cotton Cellulose with Baker's Yeast Hexokinase

Here we report for the first time on phosphorylation of cotton cellulose using baker's yeast hexokinase and phosphoryl donor adenosine‐5′‐triphosphate. An enzymatic assay was adopted for determination of the degree of phosphorylation of cellulose. This functional modification of cellulose resulted in improved colorability and flame resistance.

Phosphorylated glucopyranose unit of cellulose.     

Application of a New Dehydroascorbic Acid Reducing Agent in the Analysis of Vitamin C Content in Food

The analysis of total vitamin C content in food is most frequently performed by reducing dehydroascorbic acid to ascorbic acid, which is then assayed with the technique of high-performance liquid chromatography combined with spectrophotometric detection. Tris(2-carboxyethyl)phosphine is currently the only agent in use that efficiently reduces dehydroascorbic acid at pH < 2. Therefore, there is a continued need to search for new reducing agents that will display a high reactivity and stability in acidic solutions. The objective of the study was to verify the applicability of unithiol and tris(hydroxypropyl)phosphine for a reducing dehydroascorbic acid in an extraction medium with pH < 2. The conducted validation of the newly developed method of determining the total content of vitamin C using tris(hydroxypropyl)phosphine indicates its applicability for food analysis. The method allows obtaining equivalent results compared to the method based on the use of tris(2-carboxyethyl)phosphine. The low efficiency of dehydroascorbic acid reduction with the use of unithiol does not allow its application as a new reducing agent in vitamin C analysis.     

Transport properties of ephedrine hydrochloride through poly(vinyl alcohol) matrices—a simple method for enantiomeric differentiation

Equilibrium and transport properties have been investigated of ephedrines, a class of sympathomimetic amines, through cryogel membranes of poly(vinyl alcohol) (PVA). The effect of the PVA (10 to 18 % (w/v)) on the release properties of (1S,2R)-(+)-ephedrine hydrochloride has been discussed on the basis of partition–diffusion and power-law models. The effect of PVA concentration on the swelling degree of PVA–ephedrine matrices have been measured, allowing the estimation of the volume fraction of polymer in the gel. Ephedrine release rate constants, computed by using a first-order kinetics approach, have been modeled by using free-volume and hydrodynamic-scaling models. Differences in the release properties of the ephedrine isomers, (1S,2R)-(+)- and (1R,2S)-(?)-ephedrine as their hydrochlorides, have also been studied at different temperatures. The release kinetic constants and the corresponding activation energies show a marked discrimination between the two ephedrine isomers. This suggests that PVA cryogel membranes possess high potential for enantiomeric differentiation.     

Calorimetry in testing waste materials from the brown coal combustion

The calorimetric measurements were applied in testing the wastes collected from different furnaces in electric power plants as materials to be used in civil engineering. The fly ash materials were collected from two power stations based on different brown coal deposits and working with conventional and fluidized bed installation. The reactivity of high calcium fly ash from sub-bituminous coal combustion has been proved in calorimetric, conductometric, chemical shrinkage, and rheological measurements before their practical implementation on larger scale. Highly soluble components of fly ash contribute to the hydration products and structure formation, followed by setting and hardening of fly ash–cement mixture. These results have been the base of research project aimed in the innovative solutions dealing with the management of deposits of wastes generated as a result of coal combustion. The standardization and potential use on larger scale of these materials, necessary from the environmental point of view, seems to be the question of nearest future.     

Solid phase synthesis of two muramyl pentapeptide derivatives

Solid phase peptide synthesis (SPPS) of two selected muramyl pentapeptide derivatives is described. The simplicity of removing the protecting groups via one-step deprotection and cleavage from the resin is the biggest advantage of SPPS. Using this method, two muramyl pentapeptide derivatives, D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ser (5) and D-MurN₃-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ala (6), were obtained. Their chemical structures were confirmed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. To determine the absolute configuration of the carbon atom in the side chain of the muramic acid derivative, single-crystal X-ray diffraction measurements were recorded.     

Unprecedented Double aza‐Michael Addition within a Sapphyrin Core

A novel sapphyrin derivative was obtained from the reaction between a free‐base sapphyrin and dimethyl acetylenedicarboxylate (DMAD). The formation of the new compound involved a double aza‐Michael addition of two pyrrolic NH groups to a DMAD molecule, with the formation of a disubstituted ethano bridge. The NMR spectral data reveal a product with an unsymmetrical structure; DFT calculations provided support for a structure in which the ethano bridge links two adjacent pyrrole units. The present study provides a seemingly unprecedented example of an N,N′‐dinucleophile reacting with DMAD to form a heterocyclic compound in which the two N‐atoms are linked to the two sp³ carbon atoms derived from a substituted acetylene.