5 research outputs found
Triorganotin(IV) derivatives of 7-amino-2-(methylthio)[1,2,4]triazolo [1,5-a]pyrimidine-6-carboxylic acid. Synthesis, spectroscopic characterization, in vitro antimicrobial activity and X-ray crystallography
Triorganotin(IV) complexes of the 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic
acid (HL), Me3SnL(H2O), (1), [n-Bu3SnL]2(H2O), (2), Ph3SnL(MeOH), (3), were synthesized by reacting the
amino acid with organotin(IV) hydroxides or oxides in refluxing methanol. The complexes have been characterized
by elemental analysis, 1H, 13C and 119Sn NMR, IR, Raman and 119Sn Mössbauer spectroscopic
techniques. Single crystal X-ray diffraction data were obtained for compounds (2) and (3). Ph3SnL(MeOH)
presents a trigonal bipyramidal structure with the organic groups on the equatorial plane and the axial
positions occupied by a ligand molecule, coordinated to tin through the carboxylate, and a solvent molecule,
MeOH. A similar structure is proposed for Me3SnL(H2O) on the basis of analytical and spectroscopic
data. The tributyltin(IV) derivative, [n-Bu3SnL]2(H2O), is characterized by two different tin sites with similar
tbp geometry featured by butyl groups on the equatorial plane. Sn(1) and Sn(2) atoms are axially
bridged by a ligand molecule binding through the N(4) and the carboxylate group; the two coordination
spheres are saturated by another ligand molecule, binding the metal through the carboxylate group, and a
water molecule, respectively. Antimicrobial tests on compounds 1 and 2 showed in vitro activity against
Gram-positive bacteria
Template-assisted crystallization behavior in stirred solutions of the monoclonal antibody Anti-CD20: probability distributions of induction times
We present a method to determine the template crystallization behavior of proteins. This method is a statistical approach that accounts for the stochastic nature of nucleation. It makes use of batch-wise experiments under stirring conditions in volumes smaller than 0.3 mL to save material while mimicking larger-scale processes. To validate our method, it was applied to the crystallization of a monoclonal antibody of pharmaceutical interest, Anti-CD20. First, we determined the Anti-CD20 phase diagram in a PEG-400/Na2SO4/water system using the batch method, as, to date, no such data on Anti-CD20 solubility have been reported. Then, the probability distribution of induction times was determined experimentally, in the presence of various mesoporous silica template particles, and crystallization of Anti-CD20 in the absence of templates was compared to template-assisted crystallization. The probability distribution of induction times is shown to be a suitable method to determine the effect of template particles on protein crystallization. The induction time distribution allows for the determination of two key parameters of nucleation, the nucleation rate and the growth time. This study shows that the use of silica particles leads to faster crystallization and a higher nucleation rate. The template particle characteristics are shown to be critical parameters to efficiently promote protein crystallization