Solvent mediated phase transformations of active pharmaceutical compounds tegafur and theophylline

Elektroniskā versija nesatur pielikumusDarbā pilnveidota puskvantitatīva metode nelielu termodinamiski stabilās formas piemaisījumu daudzumu kvantificēšanai metastabilajā formā. Optimizējot paraugu sagatavošanas metodi, iespējams noteikt līdz 0,0005% termodinamiski stabilās formas metastabilajā formā. Apskatīta šķīdinātāja ietekme uz metodes jutību un, pētot šķīdinātāja desorbciju no parauga virsmas, raksturota šķīdinātāja un analizētā parauga virsmas mijiedarbība. Aprakstītas šķīdinātāja veicinātas fāžu pārejas no ftorafūra α uz β forumu un no teofilīna II uz IV formu. Noskaidrots, ka šķīdinātāja veicinātas fāžu pārejas no ftorafūra α formas uz β formu ātruma konstante ir lineāri atkarīga no pārsātinājuma pakāpes. Teofilīna IV formas rašanos kavē teofilīna molekulu paš-asociātu veidošanās protonu donoros šķīdinātājos.Here we have improved a semi-quantitative method for low-level thermodynamically stable polymorph determination in the metastable polymorph. Optimization of sample preparation methodology and conditions lowered the detection limit down to 0.0005% of thermodynamically stable form in the metastable form. Solvent effect on sample preparation have been investigated and the nature of the solvent and surface interaction have been characterized using data from solvent desorption studies. Solvent mediated phase transformations (SMPTs) from α to β tegafur and theophylline form II to IV have been studied and characterized. It was determined that SMPT rate depend linearly on the supersaturation level. It was revealed that theophylline self-associates in H-bond donor solvents and the presence of these aggregates hinder the nucleation

Structural and functional analysis of bba03, borrelia burgdorferi competitive advantage promoting outer surface lipoprotein

Publisher Copyright: © 2020 by the authors. Licensee MDPI, Basel, Switzerland. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.BBA03 is a Borrelia burgdorferi outer surface lipoprotein encoded on one of the most conserved plasmids in Borrelia genome, linear plasmid 54 (lp54). Although many of its genes have been identified as contributing or essential for spirochete fitness in vivo, the majority of the proteins encoded on this plasmid have no known function and lack homologs in other organisms. In this paper, we report the solution NMR structure of the B. burgdorferi outer surface lipoprotein BBA03, which is known to provide a competitive advantage to the bacteria during the transmission from tick vector to mammalian host. BBA03 shows structural homology to other outer surface lipoproteins reflecting their genetic and evolutionary relatedness. Analysis of the structure reveals a pore in BBA03, which could potentially bind lipids.publishersversionPeer reviewe

Aggregation Condition-Structure Relationship of Mouse Prion Protein Fibrils.

Prion diseases are associated with conformational conversion of cellular prion protein into a misfolded pathogenic form, which resembles many properties of amyloid fibrils. The same prion protein sequence can misfold into different conformations, which are responsible for variations in prion disease phenotypes (prion strains). In this work, we use atomic force microscopy, FTIR spectroscopy and magic-angle spinning NMR to devise structural models of mouse prion protein fibrils prepared in three different denaturing conditions. We find that the fibril core region as well as the structure of its N- and C-terminal parts is almost identical between the three fibrils. In contrast, the central part differs in length of β-strands and the arrangement of charged residues. We propose that the denaturant ionic strength plays a major role in determining the structure of fibrils obtained in a particular condition by stabilizing fibril core interior-facing glutamic acid residues

Peptidomimetic plasmepsin inhibitors with potent anti-malarial activity and selectivity against cathepsin D.

Following up the open initiative of anti-malarial drug discovery, a GlaxoSmithKline (GSK) phenotypic screening hit was developed to generate hydroxyethylamine based plasmepsin (Plm) inhibitors exhibiting growth inhibition of the malaria parasite Plasmodium falciparum at nanomolar concentrations. Lead optimization studies were performed with the aim of improving Plm inhibition selectivity versus the related human aspartic protease cathepsin D (Cat D). Optimization studies were performed using Plm IV as a readily accessible model protein, the inhibition of which correlates with anti-malarial activity. Guided by sequence alignment of Plms and Cat D, selectivity-inducing structural motifs were modified in the S3 and S4 sub-pocket occupying substituents of the hydroxyethylamine inhibitors. This resulted in potent anti-malarials with an up to 50-fold Plm IV/Cat D selectivity factor. More detailed investigation of the mechanism of action of the selected compounds revealed that they inhibit maturation of the P. falciparum subtilisin-like protease SUB1, and also inhibit parasite egress from erythrocytes. Our results indicate that the anti-malarial activity of the compounds is linked to inhibition of the SUB1 maturase plasmepsin subtype Plm X

Crystallization and phase transitions of ftorafur polymorphs

Darbā apskatīta daļiņu izmēra un gaisa relatīvā mitruma ietekme uz ftorafūra α- un β- fāžu pārejas kinētiku dažādās temperatūrās. Ftorafūra α- un β- kristālisko modifikāciju maisījumos abu formu saturu noteica, veicot pilna profila analīzi. Noteikta ftorafūra α- un β- līdzsvara temperatūra, izmantojot karsēšanas metodi un šķīšanas metodi, kā arī α- un γ- formu līdzsvara temperatūras, izmantojot karsēšanas metodi. Izmantojot noteiktās līdzsvara un kušanas temperatūras, aprēķināta ftorafūra β- un γ- formu līdzsvara temperatūra. Noteikti optimāli apstākļi ftorafūra ε- formas kristalizācijai no spirtu šķīdumiem.The impact of particle size and air relative humidity on tegafur α- and β- form phase transition kinetics at various temperatures is discussed in this work. The content of both forms of crystalline modifications of tegafur α- and β- polymorph mixture was determined using full profile analysis. The balance temperature of tegafur α- and β- polymorphs was defined using a heating method and solubility method, and the balance temperature of α- and γ- forms was defined using a heating method. The balance temperature of β- and γ- polymorphs was calculated from defined balance temperatures and melting temperatures. Optimal conditions of tegafur ε- form crystallization from alcohols were determined

On the Polymorph-Selective Role of Hydrogen Bonding and π - π Stacking in Para-Aminobenzoic Acid Solutions

Understanding molecular self-association in solution is vital for uncovering polymorph- selective crystal nucleation pathways. In this paper, we combine solution NMR spectroscopy and molecular dynamics simulations to shed light on the structural and dynamical features of para-aminobenzoic acid (pABA) in solution, and on their role in pABA crystals nucleation. pABA is known to yield different crystal forms (α, and β) depending on solvent choice and su- persaturation conditions. NMR reveals that dominant interactions stabilising pABA oligomers are markedly solvent-dependent: in organic solvents, hydrogen bonds dominate, while water promotes π - π stacking. Despite this clear preference, both types of interactions contribute to the variety of self-associated species in all solvents considered. MD simulations support this observation and show that pABA oligomers are short-lived and display a fluxional character, therefore indicating that the growth unit involved in pABA crystallisation is likely to be a single molecule. Nevertheless, we note that the interactions dominating in pABA oligomers are indicative of the polymorph obtained from precipitation. In water, at low pABA concen- trations - conditions that are known to yield crystals of the β form - carboxylic-carboxylic hydrogen bonds are exclusively asymmetric. At higher pABA concentration conditions in which the crystallisation is known to yield the α form - a small but statistically significant fraction of symmetric carboxylic-carboxylic hydrogen-bonded dimers is present. We interpret the presence of these interactions in solvated pABA oligomers as indicative of the fact that a simultaneous and complete desolvation of two carboxylic groups, necessary to form the sym- metric hydrogen-bonded dimer typical of the α crystal form, is accessible, therefore directing the nucleation pathway towards the nucleation of α-pABA.</div

Using HOESY NMR Spectroscopy to Characterise Pre-Nucleation Aggregates

Pre-nucleation aggregates are important species on the crystallisation pathway. Here we combine heteronuclear Overhauser effect spectroscopy (HOESY) and molecular dynamics calculations to study the self-association of a model system – benzoic acid. Our findings indicate that heteronuclear Overhauser effects arise from diffusion-limited pre-nucleation aggregates and that self-association is solvent dependant

Exploring the Binding Pathway of Novel Nonpeptidomimetic Plasmepsin V Inhibitors

Predicting the interaction modes and binding affinities of virtual compound libraries is of great interest in drug development. It reduces the cost and time of lead compound identification and selection. Here we apply path-based metadynamics simulations to characterize the binding of potential inhibitors to the Plasmodium falciparum aspartic protease plasmepsin V (plm V), a validated antimalarial drug target that has a highly mobile binding site. The potential plm V binders were identified in a high-throughput virtual screening (HTVS) campaign and were experimentally verified in a fluorescence resonance energy transfer (FRET) assay. Our simulations allowed us to estimate compound binding energies and revealed relevant states along binding/unbinding pathways in atomistic resolution. We believe that the method described allows the prioritization of compounds for synthesis and enables rational structure-based drug design for targets that undergo considerable conformational changes upon inhibitor binding

Exploring the Binding Pathway of Novel Nonpeptidomimetic Plasmepsin V Inhibitors

Predicting the interaction modes and binding affinities of virtual compound libraries is of great interest in drug development. It reduces the cost and time of lead compound identification and selection. Here we apply path-based metadynamics simulations to characterize the binding of potential inhibitors to the Plasmodium falciparum aspartic protease plasmepsin V (plm V), a validated antimalarial drug target that has a highly mobile binding site. The potential plm V binders were identified in a high-throughput virtual screening (HTVS) campaign and were experimentally verified in a fluorescence resonance energy transfer (FRET) assay. Our simulations allowed us to estimate compound binding energies and revealed relevant states along binding/unbinding pathways in atomistic resolution. We believe that the method described allows the prioritization of compounds for synthesis and enables rational structure-based drug design for targets that undergo considerable conformational changes upon inhibitor binding