Zwitterionic peptides are facile low-fouling compounds for environmental applications as they are biocompatible and fully biodegradable as their degradation products are just amino acids. Here, a set of histidine (H) and glutamic acid (E), as well as lysine (K) and glutamic acid (E) based peptide sequences with zwitterionic properties were synthesized. Both oligopeptides (KE) 4 K and (HE) 4 H were synthesized in D and L configurations to test their ability to resist the nonspecific adsorption of the proteins lysozyme and fibrinogen. The coatings were additionally tested against the attachment of the marine organisms Navicula perminuta and Cobetia marina as well as the freshwater bacterium Pseudomonas f luorescens on the developed coatings. While the peptides containing lysine performed better in protein resistance assays and against freshwater bacteria, the sequences containing histidine were generally more resistant against marine organisms. The contribution of amino acid-intrinsic properties such as side chain pK a values and hydrophobicity, as well as external parameters such as pH and salinity of fresh water and seawater on the resistance of the coatings is discussed. In this way, a detailed picture emerges as to which zwitterionic sequences show advantages in future generations of biocompatible, sustainable, and nontoxic fouling release coatings.
The effect the curing conditions on the properties of adhesive joints formed using cyanoacrylatebased adhesives is investigated. The temperature dependences of relative rigidity and mechanical loss tangent are studied by torque analysis for poly(ethyl-, allyl-, allyloxyethyl-, allyloxyisopropyl-, propargyloxyethyl-, and propargyl-) cyanoacrylates after their thermal treatment in the temperature range of 20-250 ° C. The glass transition parameters of polycyanoacrylates and the dependence of the curing intensity on the structure of initial monomers and polymers are determined. It is established that the elastic modulus decreases with the lengthening of alkyl radicals in side chains. A list is experimentally determined of monomers used to obtain adhesive compositions with stable physicomechanical properties and heat resistances of up to 250 ° C.
A new type of intramolecular electrophilic rearrangements involving the shift of COOA}k groups from carbon to an N-anionic center is considered. Carbanionic species with COOAIk groups at anionic centers containing no acidic hydrogen react unusually with atkyl(ars'l) iso(thio)cyanates giving carbamates as a result of insertion of RNCX into the C--C bond. The kinetics and mechanism of inserhon of a~'l isocyanates into the C--C bond of the phosphonium zwitterion obtained from triisopropylphosphine and ethyl 2-cyanoacrylate are discussed. The reaction of ct-carbanions derived from N,N-disubstituted amides with methyl trifluoromethanesulfonate result in O-methylation. Some possibilities of back N--*C-migrations are considered.
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