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Preservative Resistance
Published in Philip A. Geis, Cosmetic Microbiology, 2020
Enzymatic mechanisms of microorganisms are better understood than any other mechanism of preservative resistance. For example, it was reported in 1985 that five strains of Pseudomonas isolated from contaminated cosmetic products were resistant to high concentrations of imidazolidinyl urea (5). In each of these contaminated products, imidazolidinyl urea had been metabolized to formaldehyde which in turn was metabolized to a UV-absorbing lutidine derivative. In addition to imidazolidinyl urea, Pseudomonas aeruginosa isolates have also been found to be resistant to the antimicrobial activity of DMDM hydantoin, another formaldehyde-releasing preservative. These resistant isolates were found to have typical patterns of outer membrane proteins (8). It was determined that the development of these Pseudomonas aeruginosa-resistant strains was not due to a reduced permeation of DMDM hydantoin or other formaldehyde-releasing preservative across the outer membrane of the bacterial cell, but due to the enzyme formaldehyde dehydrogenase that is able to metabolize formaldehyde to formic acid that is ineffective as a cosmetic/personal care preservative (15,16).
Detection And Identification of Drugs of Dependence
Published in S.J. Mulé, Henry Brill, Chemical and Biological Aspects of Drug Dependence, 2019
A spectrofluorometric procedure for the determination of amphetamine alone or in combination with other drugs was developed by Nix and Hume.134 The determination was based upon the reaction of amphetamine with formaldehyde and acetylacetone to produce a fluorophore. The excitation and emission wavelengths of the lutidine derivative (fluorophore) of amphetamine were determined at 415 nm and 482 nm, respectively. The minimal detection limit was 0.26 μg/ml. Interference with this determination was observed with methamphetamine and phenethyl-amine.
Process parameters of microsphere preparation based on propylene carbonate emulsion-precursors
Published in Journal of Microencapsulation, 2021
The residual PC content was analysed using a previously described HOC method (Grizić et al.2016), which is based on a sequential chemical conversion of PC into 3,5-diacetyl-1,4-dihydro-2,6-lutidine by stepwise hydrolysis (H), oxidation (O) and condensation (C) reactions. In this way, residual PC amounts could be quantified. For this purpose, 20 mg of microspheres were dissolved in 200 µL of glycofurol, followed by the addition of 1800 µL of distilled water which led to PLGA precipitation. The mixture was filtered using a 0.2 µm polypropylene membrane filter and further analysed, expressing the results as PC percentage in the microspheres [w/w].
First studies on tumor associated carbonic anhydrases IX and XII monoclonal antibodies conjugated to small molecule inhibitors
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Chiara Testa, Anna Maria Papini, Reinhard Zeidler, Daniela Vullo, Fabrizio Carta, Claudiu T. Supuran, Paolo Rovero
The peptide precursors A and B were synthesised on Fmoc-Cys(Trt)-Wang resin (0.57 mmol/g, 500 mg), on a manual batch synthesiser (PLS 4 × 4, Advanced ChemTech), following the Fmoc/tBu chemistry. The resin was swelled with DMF (1 ml/100 mg of resin) for 20 min before use. Stepwise peptide assembly was performed by repeating deprotection-coupling cycles with the required amino acids. In brief: (a) Swelling: DMF (1 ml/100 mg of resin) for 5 min. (b) Fmoc-deprotection: resin washing with 20% (v/v) piperidine in DMF (1 ml/100 mg of resin, one wash for 5 min, followed by another wash for 20 min). (c) Resin washing: DMF (3–5 min). (d) Coupling: HBTU/NMM (5.0/7.0 equiv.) as coupling system and 5 eq. of the Fmoc-protected amino acids, except for the non-coded amino acids Fmoc-L-Ala(β-N3)-OH and Na-Fmoc-L-Pra-OH, for which 2.5 eq. were used. The coupling was carried out in DMF (1 ml/100 mg of resin) for 50 min. (e) Resin washings: DMF (3–5 min) and DCM (1–5 min). Each coupling was monitored by Kaiser test and was negative at completion, therefore recouplings were not needed. The resin-bound peptide was subjected to solid-phase Cu(I)-catalysed azide-alkyne 1,3-dipolar Huisgen cycloaddition (CuAAC). To the dry resin bound peptide in a fritted syringe were added CuI (1.0 eq), sodium ascorbate dissolved in water (1.0 eq.), the appropriate CAI-alkynyl 1a–3a or CAI-azide 4a–7a section (1.0 eq.), DIPEA (10.0 eq.), and 2,6-lutidine (10.0 eq.) in 1 ml DMF. After 18 h at r.t. the resin was filtered and washed with DMF and DCM. Peptide cleavage from the resin was carried out by shaking the peptidyl resin for 3 h at room temperature in a mixture of TFA/anisole/1,2-ethanedithiol/phenol/H2O (94:1:1:1:1, v/v/v/v/v, 1 ml/100 mg of resin-bound peptide). This led also to the deprotection of the amino acid side chains. Resin was filtered and washed with TFA. The crude peptide was recovered by centrifugation after concentration of the filtrate under N2 stream and precipitation by addition of cold diethyl ether. The pellet was dissolved in H2O and freeze-dried. The lyophilised crude peptides were partially purified by solid-phase extraction and then purified by semipreparative RP-HPLC with a linear solvent gradient of 0.5%–50% B in A in 20 min. The final chromatographic purity of all peptides was ≥95%. Peptides were characterised by RP-HPLC-ESI-MS.