Synthesis of N-succinyl- and N-glutaryl-chitosan derivatives and their antioxidant, antiplatelet, and anticoagulant activity.

The effects of temperature, reactant ratio, pH, and reaction time were studied on the polymers formed by the reactions of succinic and glutaric anhydrides with chitosan under both homogeneous and heterogeneous conditions. As a result, protocols were developed for the synthesis of succinyl- and glutaryl-chitosan derivatives (SC and GC, respectively) with a specific degree of substitution. The polymers were characterized by NMR spectroscopy, including two-dimensional NMR techniques, that confirms N-substitution of chitosan under reaction conditions used. SC and GC both show pronounced and similar antioxidant activity, which slightly increases with an increase in the degree of substitution. Both SC and GC showed antiplatelet and anticoagulant activity. The platelet aggregation is suppressed more strongly in the experiments with GC than with SC, although the latter exhibits a more pronounced anticoagulant activity.

Fluorescent and Photosensitizing Conjugates of Cell-Penetrating Peptide TAT(47-57): Design, Microwave-Assisted Synthesis at 60 °C, and Properties.

Conjugates based on cell-penetrating peptides (CPPs) are scientifically relevant owing to their structural complexity; their ability to enter cells and deliver drugs, labels, antioxidants, bioactive compounds, or DNA fragments; and, consequently, their potential for application in research and biomedicine. In this study, carboxyamidated fluorescently labeled conjugates FAM-GG-TAT(47-57)-NH2 and FAM-PEG6-TAT(47-57)-NH2 and photosensitizer-labeled conjugate Chk-PEG6-TAT(47-57)-NH2 [where TAT(47-57) is the CPP, 5(6)-carboxyfluorescein is the (FAM) fluorophore, chlorin k (Chk) is the photosensitizer, and the dipeptide glycyl-glycine (GG) or hexaethylene glycol (PEG6) is the spacer] were originally designed, prepared, and fully characterized. Practically, all chemical reactions of the synthetic steps (peptide synthesis, spacer incorporation, and conjugation) were microwave-assisted at 60 °C using optimized protocols to give satisfying yields and high-quality products. Detailed analyses of the conjugates using spectrofluorimetry and singlet oxygen detection showed that they display photophysical properties typical of FAM or Chk. Anticandidal activity assays showed that not only this basic property of TAT(47-57) was preserved in the conjugates but also that the minimal inhibitory concentration was slightly reduced for cells incubated with PS-bearing conjugate Chk-PEG6-TAT(47-57)-NH2. Overall, these results indicated that the synthetic approach on-resin assisted by microwaves at 60 °C is simple, straightforward, selective, metal-free, sufficiently fast, cleaner, and more cost-effective than those previously used for preparing this type of macromolecule. Furthermore, such new data show that microwaves at 60 °C and/or conjugation did not harm the integrity of the conjugates' constituents. Therefore, FAM-GG-TAT(47-57)-NH2, FAM-PEG6-TAT(47-57)-NH2, and Chk-PEG6-TAT(47-57)-NH2 have high potential for practical applications in biochemistry, biophysics, and therapeutics.

O,N-(2-sulfoethyl)chitosan: Synthesis and properties of solutions and films.

A series of water-soluble sulfoethylated chitosans (SEC) with degrees of substitution (DS) up to 130% were obtained using a heterogeneous reaction of chitosan with sodium 2-chloroethanesulfonate in 85% isopropanol in the presence of NaOH. NMR and FTIR spectroscopy confirmed that sulfoethylation of chitosan preferentially happens at hydroxyl groups and to some extent at amino groups, giving mixed substituted O,N-SEC. Chitosan shows positive birefringence, whereas SEC shows negative values, indicating self-organization in dilute solution. Dynamic light scattering studies revealed the presence of aggregates in dilute solutions of chitosan and SEC. The sizes of the SEC aggregates are sensitive to the DS and the nature of the solvent. X-ray diffraction of SEC films revealed that the introduction of sulfoethyl groups into chitosan leads to amorphization, which is more pronounced at higher DS. During the storage of SEC films, the samples loose solubility due to the formation of ionic crosslinks upon dehydration.

Chemically synthesized and cross-linked PDMS as versatile alignment medium for organic compounds.

A useful procedure for the preparation of chemically synthesized and cross-linked polydimethylsiloxane (PDMS) gels is presented, which does not require ß-irradiation for cross-linking. NMR spectra of high quality are obtained, such that even mixtures of compounds exhibiting similar NMR spectra like interconverting stereoisomers can be investigated in the residual dipolar coupling (RDC) approach of organic structure determination.

One-end nucleophilic addition of di- and triamines to Pt(IV)-coordinated nitriles as an entry to (amidine)Pt(IV) complexes bearing pendant NH2-groups.

The reactions of trans-[PtCl4(RCN)2] (R= Me, Et, CH2Ph, Ph) with the diamines and the triamine NH2{spacer}NH2 (spacer = CH2CH2, CH(Me)CH2, CH2CH2CH2, CH2CH2CH2CH2, CH2CH2NHCH2CH2) in a molar ratio 1 : 2 produce trans-[PtCl4{NH=C(R)NH{spacer}NH2}2] (spacer/R = CH2CH2/Et 1, CH2CHMe/Et 2 (a mixture of regioisomers), CH2CH2CH2/Et 3, CH2CH2CH2CH2/Et 4, CH2CH2/Me 5, CH2CH2/CH2Ph 6, CH2CH2/Ph 7, CH2CH2NHCH2CH2/Et 8) with the monodentately coordinated amidine ligands having the pendant NH2 groups. The complexes have been characterised by C, H, and N elemental analyses, ¹³C CP-MAS NMR and IR spectroscopy, (TOF)-ESI-MS, and [1·H2](Pic)2·EtOH also by X-ray diffraction.