Influence Of Side-chain Structure Research Articles

Influence of side chain structure on the thermal and antimicrobial properties of cationic methacrylic polymers

A novel methacrylic monomer, 2-(((2-(4-methylthiazol-5-yl)ethoxy)carbonyl)oxy)ethyl methacrylate (MTZ), containing in the lateral chain both hydrolytically sensitive carbonate and thiazole groups has been firstly described. Posterior, it was free-radical polymerized and copolymerized with acrylonitrile in anhydrous solution of dimethylsulfoxide, with the purpose of investigate the influence of its chemical and structural characteristics on the antimicrobial activity. Cationic antimicrobial polymers were subsequently obtained by alkylation reaction with methyl and butyl iodide agents. Their thermal behavior was analyzed in all series, modified and unmodified copolymers in terms of glass transition temperature and thermal stability. The antimicrobial activity in solution was tested against Gram-positive Staphylococcus aureus and Staphylococcus epidermidis, Gram-negative Escherichia coli and Pseudomonas aeruginosa bacteria, and Candida parapsilosis yeast and further correlated with their zeta potential. Then, blends of these cationic polymers with commercial polyacrylonitrile as matrix material were prepared and their effectiveness as antimicrobial coating was determined against Gram-negative Escherichia coli bacteria. In addition and due to the presence of the carbonate groups in the copolymer structures, these systems could be further used as antimicrobial releasing coatings in alkaline conditions.

Bis-3-chloropiperidines containing bridging lysine linkers: Influence of side chain structure on DNA alkylating activity

A series of bis-3-chloropiperidines containing lysine linkers was synthesised as DNA alkylating model compounds by using a bidirectional synthetic strategy. These novel piperidine mustard based agents have been evaluated for their alkylating properties towards nucleic acids and were shown to alkylate and cleave DNA with strong preference for guanine residues. Our studies reveal that the introduction of aromatic groups in the side chain of the lysine linker has an impact on DNA alkylating activity. Analysis by ESI mass spectrometry enabled the verification of the reactive aziridinium ion formation. Overall, the results confirm our recently proposed reaction mechanism of bis-3-chloropiperidines.

Mechanistic studies of melanogenesis: the influence of N‐substitution on dopamine quinone cyclization

The influence of side-chain structure on the mode of reaction of ortho-quinone amines has been investigated with a view, ultimately, to developing potential methods of therapeutic intervention by manipulating the early stages of melanogenesis. Four N-substituted dopamine derivatives have been prepared and quinone formation studied using pulse radiolysis and tyrosinase-oximetry. Ortho-quinones with an amide or urea side chain were relatively stable, although evidence for slow formation of isomeric para-quinomethanes was observed. A thiourea derivative cyclized fairly rapidly (k = 1.7/s) to a product containing a seven-membered ring, whereas a related amidine gave more rapidly (k approximately 2.5 x 10(2)/s) a stable spirocyclic product. The results suggest that cyclization of amides, ureas and carbamates (NHCO-X; X = R, NHR or OR) does not occur and is not, therefore, a viable approach to the formation of tyrosinase-activated antimelanoma prodrugs. It is also concluded that for N-acetyldopamine spontaneous ortho-quinone to para-quinomethane isomerization is slow.

Influence of side chain structure on sorption of xenon and carbon dioxide gas by polypeptide membranes

The influence of side chain structure on sorption of xenon and carbon dioxide gas by polypeptides is examined in two ways: chemical structure of side chain and higher order structure of the side chain region. Sorption of xenon gas increases progressively with increase in side chain length of poly(n-alkyl L-glutamates). The sorption isotherms of a polymer at various temperatures are reduced to one curve when the data are arranged in the form of sorption per residue versus fugacity ratio (as activity). The sorption of carbon dioxide gas shows a minimum at an intermediate length of side chains, corresponding to poly(n-propyl or n-butyl glutamate). The behavior is considered the result of overlapping influences of looseness of the side chain region and density of polar groups. The Langmuir constants and the enthalpy and entropy of sorption explain this quantitatively. Sorption of carbon dioxide gas is influenced by the higher-order structure of poly(γ-benzyl L-glutamate). In this polymer, the benzyl ester part is the main sorption site, and it was confirmed that the stacking between side-chain benzene rings significantly reduces the extent of sorption.