Structural basis for enantiomer binding and separation of a common beta-blocker: crystal structure of cellobiohydrolase Cel7A with bound (S)-propranolol at 1.9 A resolution

Environmental benign catalyst developed by fruit waste for synthesis of β-amino alcohol with the optimum combination through statistical analysis

An Eco-catalysis approach reported in this manuscript, is developed by the kinnow peel waste as the green catalyst for the ring opening of epichlorohydrin with aromatic amines and its derivatives. The prepared green catalyst is used in three different variants i.e. kinnow peel powder (KPP), Bare component, and ash of KPP. Prepared catalyst characterized by TEM, SEM-EDX, FTIR, TGA, and XRD. Statistical analysis is a full factorial analysis of variance technique to identify the optimum combinations of types of catalyst, catalyst quantity, and derivative type.

A workflow to create a high-quality protein-ligand binding dataset for training, validation, and prediction tasks

Development of scoring functions (SFs) used to predict protein-ligand binding energies requires high-quality 3D structures and binding assay data for training and testing their parameters. In this work, we show that one of the widely-used datasets, PDBbind, suffers from several common structural artifacts of both proteins and ligands, which may compromise the accuracy, reliability, and generalizability of the resulting SFs. Therefore, we have developed a series of algorithms organized in a semi-automated workflow, HiQBind-WF, that curates non-covalent protein-ligand datasets to fix these problems. We also used this workflow to create an independent data set, HiQBind, by matching binding free energies from various sources including BioLiP, Binding MOAD and Binding DB with co-crystalized ligand-protein complexes from the PDB. The resulting HiQBind workflow and dataset are designed to ensure reproducibility and to minimize human intervention, while also being open-source to foster transparency in the improvements made to this important resource for the biology and drug discovery communities.

Biomimetic separations in chemistry and life sciences

Since Otto Schmitt introduced the term "biomimetics" in 1957, the imitation of biological systems to develop separation methods and simulate biological processes has seen continuous growth, particularly over the past five decades. The biomimetic approach relies on the use of specific ligands-biospecific, biomimetic, or synthetic-which target biomolecules, such as proteins, antibodies, nucleic acids, enzymes, drugs, pesticides, and other bioactive analytes. This review highlights advances in biomimetic separations, focusing on biomimetic liquid chromatography (including immobilized artificial membrane chromatography, cell membrane chromatography, biomimetic affinity chromatography, weak affinity chromatography, micellar liquid chromatography, immobilized liposome chromatography, and liposome electrokinetic capillary chromatography) for the complex separation and purification of biomolecules and other important chemical compounds. It also explores their application in studying drug-receptor interactions, screening chemical permeability, absorption, distribution, toxicity, as well as predicting environmental risks. Additionally, this review discusses the application of biomimetic magnetic nanoparticles, which leverage biological membranes and proteins for drug discovery, protein purification, and diagnostics.

Pd/C-Catalyzed Tandem Synthesis of β-Amino Alcohol Using Epoxide through Transfer Hydrogenation of Nitroarene with Methanol

Using commercially available Pd/C as a catalyst, β-amino alcohols are synthesized from nitroarenes and 1,2-epoxides. Nitroarenes are transformed to amines through ring opening of epoxides and transfer hydrogenation of methanol over the Pd/C catalyst, producing β-amino alcohols. This approach generates aniline in situ from nitrobenzene, making it a viable alternative to traditional β-amino alcohol synthesis procedures. This technique has advantages, including easy recovery of catalysts through filtration and elimination of the requirement for intermediate separation.

Update on chiral recognition mechanisms in separation science

The stereospecific analysis of chiral molecules is an important issue in many scientific fields. In separation sciences, this is achieved via the formation of transient diastereomeric complexes between a chiral selector and the selectand enantiomers driven by molecular interactions including electrostatic, ion-dipole, dipole-dipole, van der Waals or π-π interactions as well as hydrogen or halogen bonds depending on the nature of selector and selectand. Nuclear magnetic resonance spectroscopy and molecular modeling methods are currently the most frequently applied techniques to understand the selector-selectand interactions at a molecular level and to draw conclusions on the chiral separation mechanism. The present short review summarizes some of the recent achievements for the understanding of the chiral recognition of the most important chiral selectors combining separation techniques with molecular modeling and/or spectroscopic techniques dating between 2020 and early 2024. The selectors include polysaccharide derivatives, cyclodextrins, macrocyclic glycopeptides, proteins, donor-acceptor type selectors, ion-exchangers, crown ethers, and molecular micelles. The application of chiral ionic liquids and chiral deep eutectic solvents, as well as further selectors, are also briefly addressed. A compilation of all published literature on chiral selectors has not been attempted.

Brønsted Acid-Catalysed Epoxide Ring-Opening Using Amine Nucleophiles: A facile access to β-amino alcohols

A mild, efficient, and metal-free synthetic protocol for the synthesis of β-amino alcohols is reported. The reaction proceeds at room temperature with only 0.5 mol% catalyst loading and affords β-amino alcohol derivatives in excellent yield. This protocol is well-tolerated by a wide range of styrene oxide and aniline derivatives. A notably efficacious gram-scale synthesis is also reported with a high TON = 842. Further, the Hammett correlation study was also performed to identify the rate-determining step.

Metal-Free β-Amino Alcohol Synthesis: A Two-step Smiles Rearrangement

A novel method for the synthesis of β-amino alcohols has been demonstrated under mild reaction conditions with a broad scope via a two-step Smiles rearrangement. What is more, theoretical calculations have been performed to confirm the rationality of the mechanism. The method has been proved to be notably effective for N-arylated amino alcohols, which are difficult to synthesize by traditional methods.

Ring-Opening of Epoxides with Amines for Synthesis of β-Amino Alcohols in a Continuous-Flow Biocatalysis System

An efficient method for the preparation of β-amino alcohols catalyzed by lipase TL IM from Thermomyces lanuginosus in a continuous-flow reactor was developed. The eco-friendly biocatalyst combined with continuous-flow reaction technology displayed high efficiency in the synthesis of β-amino alcohols. The benign reaction conditions (35 °C) and short residence time (20 min), together with the use of low cost and readily available starting materials, make this synthetic approach a promising alternative to current β-amino alcohol synthesis.

Affinity chromatography: A review of trends and developments over the past 50 years

The field of affinity chromatography, which employs a biologically-related agent as the stationary phase, has seen significant growth since the modern era of this method began in 1968. This review examines the major developments and trends that have occurred in this technique over the past five decades. The basic principles and history of this area are first discussed. This is followed by an overview of the various supports, immobilization strategies, and types of binding agents that have been used in this field. The general types of applications and fields of use that have appeared for affinity chromatography are also considered. A survey of the literature is used to identify major trends in these topics and important areas of use for affinity chromatography in the separation, analysis, or characterization of chemicals and biochemicals.

An insight into chiral monolithic stationary phases for enantioselective high-performance liquid chromatography applications

In this review, three main classes of chiral monolithic stationary phases, namely silica-, organic polymer-, and hybrid-based monolithic stationary phases, are covered. Their preparations, applications, and advantages compared with the conventional-packed and open-tubular capillary columns are discussed. A detailed description of the different types and techniques used for the introduction of chiral selectors into the monolithic matrices such as immobilization, functionalization, coating, encapsulation, and bonding. Special emphasis is given to the recent developments of chiral selectors in HPLC monolithic stationary phases during the past 18 years.

Enhancing Enzymatic Properties of Endoglucanase I Enzyme from Trichoderma Reesei via Swapping from Cellobiohydrolase I Enzyme

Utilizing plant-based materials as a biofuel source is an increasingly popular attempt to redesign the global energy cycle. This endeavour underlines the potential of cellulase enzymes for green energy production and requires the structural and functional engineering of natural enzymes to enhance their utilization. In this work, we aimed to engineer enzymatic and functional properties of Endoglucanase I (EGI) by swapping the Ala43-Gly83 region of Cellobiohydrolase I (CBHI) from Trichoderma reesei. Herein, we report the enhanced enzymatic activity and improved thermal stability of the engineered enzyme, called EGI_swapped, compared to EGI. The difference in the enzymatic activity profile of EGI_swapped and the EGI enzymes became more pronounced upon increasing metal-ion concentrations in the reaction media. Notably, the engineered enzyme retained a considerable level of enzymatic activity after thermal incubation for 90 min at 70 °C while EGI completely lost its enzymatic activity. Circular Dichroism spectroscopy studies revealed distinctive conformational and thermal susceptibility differences between EGI_swapped and EGI enzymes, confirming the improved structural integrity of the swapped enzyme. This study highlights the importance of swapping the metal-ion coordination region in the engineering of EGI enzyme for enhanced structural and thermal stability.

Enantioselective Binding of Propranolol and Analogues Thereof to Cellobiohydrolase Cel7A

At the catalytic site for the hydrolysis of cellulose the enzyme cellobiohydrolase Cel7A binds the enantiomers of the adrenergic beta-blocker propranolol with different selectivity. Methyl-to-hydroxymethyl group modifications of propranolol, which result in higher affinity and improved selectivity, were herein studied by ¹ H,¹ H and ¹ H,¹³ C scalar spin-spin coupling constants as well as utilizing the nuclear Overhauser effect (NOE) in conjunction with molecular dynamics simulations of the ligands per se, which showed the presence of all-antiperiplanar conformations, except for the one containing a vicinal oxygen-oxygen arrangement governed by the gauche effect. For the ligand-protein complexes investigated by NMR spectroscopy using, inter alia, transferred NOESY and saturation-transfer difference (STD) NMR experiments the S-isomers were shown to bind with a higher affinity and a conformation similar to that preferred in solution, in contrast to the R-isomer. The fact that the S-form of the propranolol enantiomer is pre-arranged for binding to the protein is also observed for a crystal structure of dihydroxy-(S)-propranolol and Cel7A presented herein. Whereas the binding of propranolol is entropy driven, the complexation with the dihydroxy analogue is anticipated to be favored also by an enthalpic term, such as for its enantiomer, that is, dihydroxy-(R)-propranolol, because hydrogen-bond donation replaces the corresponding bonding from hydroxyl groups in glucosyl residues of the natural substrate. In addition to a favorable entropy component, albeit lesser in magnitude, this represents an effect of enthalpy-to-entropy compensation in ligand-protein interactions.

High performance affinity chromatography and related separation methods for the analysis of biological and pharmaceutical agents

The last few decades have witnessed the development of many high-performance separation methods that use biologically related binding agents. The combination of HPLC with these binding agents results in a technique known as high performance affinity chromatography (HPAC). This review will discuss the general principles of HPAC and related techniques, with an emphasis on their use for the analysis of biological compounds and pharmaceutical agents. Various types of binding agents for these methods will be considered, including antibodies, immunoglobulin-binding proteins, aptamers, enzymes, lectins, transport proteins, lipids, and carbohydrates. Formats that will be discussed for these methods range from the direct detection of an analyte to indirect detection based on chromatographic immunoassays, as well as schemes based on analyte extraction or depletion, post-column detection, and multi-column systems. The use of biological agents in HPLC for chiral separations will also be considered, along with the use of HPAC as a tool to screen or study biological interactions. Various examples will be presented to illustrate these approaches and their applications in fields such as biochemistry, clinical chemistry, and pharmaceutical research.

Impact of assay temperature on antibody binding characteristics in living cells: A case study

Kinetic and thermodynamic studies of ligand-receptor interactions are essential for increasing the understanding of receptor activation mechanisms and drug behavior. The characterization of molecular interactions on living cells in real-time goes beyond most current binding assays, and provides valuable information about the dynamics and underlying mechanism of the molecules in a living system. The effect of temperature on interactions in cell-based assays is, however, rarely discussed. In the present study, the effect of temperature on binding of monoclonal antibodies, cetuximab and pertuzumab to specific receptors on living cancer cells was evaluated, and the affinity and kinetics of the interactions were estimated at selected key temperatures. Changes in the behavior of the interactions, particularly in the on- and off-rates were observed, leading to greatly extended time to reach the equilibrium at 21°C compared with at 37°C. However, the observed changes in kinetic characteristics were less than a factor of 10. It was concluded that it is possible to conduct real-time measurements with living cells at different temperatures, and demonstrated that influences of the ambient temperature on the interaction behavior are likely to be less than one order of magnitude.

Functioning of drug-metabolizing microsomal cytochrome P450s: In silico probing of proteins suggests that the distal heme 'active site' pocket plays a relatively 'passive role' in some enzyme-substrate interactions

PURPOSE

The currently held mechanistic understanding of microsomal cytochrome P450s (CYPs) seeks that diverse drug molecules bind within the deep-seated distal heme pocket and subsequently react at the heme centre. To explain a bevy of experimental observations and meta-analyses, we indulge a hypothesis that involves a "diffusible radical mediated" mechanism. This new hypothesis posits that many substrates could also bind at alternate loci on/within the enzyme and be reacted without the pertinent moiety accessing a bonding proximity to the purported catalytic Fe-O enzyme intermediate.

METHODS

Through blind and heme-distal pocket centered dockings of various substrates and non-substrates (drug molecules of diverse sizes, classes, topographies etc.) of microsomal CYPs, we explored the possibility of access of substrates via the distal channels, its binding energies, docking orientations, distance of reactive moieties (or molecule per se) to/from the heme centre, etc. We investigated specific cases like- (a) large drug molecules as substrates, (b) classical marker drug substrates, (c) class of drugs as substrates (Sartans, Statins etc.), (d) substrate preferences between related and unrelated CYPs, (e) man-made site-directed mutants' and naturally occurring mutants' reactivity and metabolic disposition, (f) drug-drug interactions, (g) overall affinities of drug substrate versus oxidized product, (h) meta-analysis of in silico versus experimental binding constants and reaction/residence times etc.

RESULTS

It was found that heme-centered dockings of the substrate/modulator drug molecules with the available CYP crystal structures gave poor docking geometries and distances from Fe-heme centre. In conjunction with several other arguments, the findings discount the relevance of erstwhile hypothesis in many CYP systems. Consequently, the newly proposed hypothesis is deemed a viable alternate, as it satisfies Occam's razor.

CONCLUSIONS

The new proposal affords expanded scope for explaining the mechanism, kinetics and overall phenomenology of CYP mediated drug metabolism. It is now understood that the heme-iron and the hydrophobic distal pocket of CYPs serve primarily to stabilize the reactive intermediate (diffusible radical) and the surface or crypts of the apoprotein bind to the xenobiotic substrate (and in some cases, the heme distal pocket could also serve the latter function). Thus, CYPs enhance reaction rates and selectivity/specificity via a hitherto unrecognized modality.

Separation of enantiomers on chiral stationary phase based on cellulase: Effect of preparation method and silica particle diameters on chiral recognition ability

Cellulase (Cel) was immobilized onto aminopropyl-silica gels via its amino and carboxy groups, respectively, using N,N'-disuccinimidyl carbonate, and 1-ethyl-3-(3'-dimethylaminopropyl)carbodimide and N-hydroxysulfosuccinimide. They were termed N-Cel and C-Cel, respectively. Despite their smaller retention factors on a C-Cel column, the enantioseparation factors and resolution of β-blockers, propranolol, alprenolol, oxprenolol and pindolol, were similar with N- and C-Cel columns. In addition, C-Cel was prepared using aminopropyl-silica gels, whose nominal particle diameters were 5 and 3, and 2.1μm, respectively. A C-Cel column prepared with 2.1-μm aminopropyl-silica gels gave the highest enantioselectivity and column efficiency among three C-Cel columns. Furthermore, the influence of N,N-dimethyl-n-octylamine (DMOA) or cellobiose concentrations on the retentivity and enantioselectivity for β-blockers on a C-Cel column was investigated. The results indicate that single-site competition of β-blockers with DMOA or cellobiose on the catalytic binding site of Cel and the further bindings at the secondary site in a non-competitive fashion could occur. Furthermore, the enantioselective bindings of β-blockers could occur at the catalytic biding cite of Cel and at the secondary binding site.

Biochemical and Structural Characterizations of Two Dictyostelium Cellobiohydrolases from the Amoebozoa Kingdom Reveal a High Level of Conservation between Distant Phylogenetic Trees of Life

Glycoside hydrolase family 7 (GH7) cellobiohydrolases (CBHs) are enzymes commonly employed in plant cell wall degradation across eukaryotic kingdoms of life, as they provide significant hydrolytic potential in cellulose turnover. To date, many fungal GH7 CBHs have been examined, yet many questions regarding structure-activity relationships in these important natural and commercial enzymes remain. Here, we present the crystal structures and a biochemical analysis of two GH7 CBHs from social amoeba: Dictyostelium discoideum Cel7A (DdiCel7A) and Dictyostelium purpureum Cel7A (DpuCel7A). DdiCel7A and DpuCel7A natively consist of a catalytic domain and do not exhibit a carbohydrate-binding module (CBM). The structures of DdiCel7A and DpuCel7A, resolved to 2.1 Å and 2.7 Å, respectively, are homologous to those of other GH7 CBHs with an enclosed active-site tunnel. Two primary differences between the Dictyostelium CBHs and the archetypal model GH7 CBH, Trichoderma reesei Cel7A (TreCel7A), occur near the hydrolytic active site and the product-binding sites. To compare the activities of these enzymes with the activity of TreCel7A, the family 1 TreCel7A CBM and linker were added to the C terminus of each of the Dictyostelium enzymes, creating DdiCel7ACBM and DpuCel7ACBM, which were recombinantly expressed in T. reesei DdiCel7ACBM and DpuCel7ACBM hydrolyzed Avicel, pretreated corn stover, and phosphoric acid-swollen cellulose as efficiently as TreCel7A when hydrolysis was compared at their temperature optima. The Ki of cellobiose was significantly higher for DdiCel7ACBM and DpuCel7ACBM than for TreCel7A: 205, 130, and 29 μM, respectively. Taken together, the present study highlights the remarkable degree of conservation of the activity of these key natural and industrial enzymes across quite distant phylogenetic trees of life.

IMPORTANCE

GH7 CBHs are among the most important cellulolytic enzymes both in nature and for emerging industrial applications for cellulose breakdown. Understanding the diversity of these key industrial enzymes is critical to engineering them for higher levels of activity and greater stability. The present work demonstrates that two GH7 CBHs from social amoeba are surprisingly quite similar in structure and activity to the canonical GH7 CBH from the model biomass-degrading fungus T. reesei when tested under equivalent conditions (with added CBM-linker domains) on an industrially relevant substrate.

Carbohydrate-protein interactions that drive processive polysaccharide translocation in enzymes revealed from a computational study of cellobiohydrolase processivity

Translocation of carbohydrate polymers through protein tunnels and clefts is a ubiquitous biochemical phenomenon in proteins such as polysaccharide synthases, glycoside hydrolases, and carbohydrate-binding modules. Although static snapshots of carbohydrate polymer binding in proteins have long been studied via crystallography and spectroscopy, the molecular details of polysaccharide chain processivity have not been elucidated. Here, we employ simulation to examine how a cellulose chain translocates by a disaccharide unit during the processive cycle of a glycoside hydrolase family 7 cellobiohydrolase. Our results demonstrate that these biologically and industrially important enzymes employ a two-step mechanism for chain threading to form a Michaelis complex and that the free energy barrier to chain threading is significantly lower than the hydrolysis barrier. Taken with previous studies, our findings suggest that the rate-limiting step in enzymatic cellulose degradation is the glycosylation reaction, not chain processivity. Based on the simulations, we find that strong electrostatic interactions with polar residues that are conserved in GH7 cellobiohydrolases, but not in GH7 endoglucanases, at the leading glucosyl ring provide the thermodynamic driving force for polysaccharide chain translocation. Also, we consider the role of aromatic-carbohydrate interactions, which are widespread in carbohydrate-active enzymes and have long been associated with processivity. Our analysis suggests that the primary role for these aromatic residues is to provide tunnel shape and guide the carbohydrate chain to the active site. More broadly, this work elucidates the role of common protein motifs found in carbohydrate-active enzymes that synthesize or depolymerize polysaccharides by chain translocation mechanisms coupled to catalysis.

Computational investigation of the pH dependence of loop flexibility and catalytic function in glycoside hydrolases

Cellulase enzymes cleave glycosidic bonds in cellulose to produce cellobiose via either retaining or inverting hydrolysis mechanisms, which are significantly pH-dependent. Many fungal cellulases function optimally at pH ~5, and their activities decrease dramatically at higher or lower pH. To understand the molecular-level implications of pH in cellulase structure, we use a hybrid, solvent-based, constant pH molecular dynamics method combined with pH-based replica exchange to determine the pK(a) values of titratable residues of a glycoside hydrolase (GH) family 6 cellobiohydrolase (Cel6A) and a GH family 7 cellobiohydrolase (Cel7A) from the fungus Hypocrea jecorina. For both enzymes, we demonstrate that a bound substrate significantly affects the pKa values of the acid residues at the catalytic center. The calculated pK(a) values of catalytic residues confirm their proposed roles from structural studies and are consistent with the experimentally measured apparent pKa values. Additionally, GHs are known to impart a strained pucker conformation in carbohydrate substrates in active sites for catalysis, and results from free energy calculations combined with constant pH molecular dynamics suggest that the correct ring pucker is stable near the optimal pH for both Cel6A and Cel7A. Much longer molecular dynamics simulations of Cel6A and Cel7A with fixed protonation states based on the calculated pK(a) values suggest that pH affects the flexibility of tunnel loops, which likely affects processivity and substrate complexation. Taken together, this work demonstrates several molecular-level effects of pH on GH enzymes important for cellulose turnover in the biosphere and relevant to biomass conversion processes.

Chiral recognition in separation science: an overview

Chiral recognition phenomena play an important role in nature as well as analytical separation sciences. In separation sciences such as chromatography and capillary electrophoresis, enantiospecific interactions between the enantiomers of an analyte and the chiral selector are required in order to observe enantioseparations. Due to the large structural variety of chiral selectors applied, different mechanisms and structural features contribute to the chiral recognition process. This chapter briefly illustrates the current models of the enantiospecific recognition on the structural basics of various chiral selectors.

Chiral recognition by enantioselective liquid chromatography: mechanisms and modern chiral stationary phases

An overview of the state-of-the-art in LC enantiomer separation is presented. This tutorial review is mainly focused on mechanisms of chiral recognition and enantiomer distinction of popular chiral selectors and corresponding chiral stationary phases including discussions of thermodynamics, additivity principle of binding increments, site-selective thermodynamics, extrathermodynamic approaches, methods employed for the investigation of dominating intermolecular interactions and complex structures such as spectroscopic methods (IR, NMR), X-ray diffraction and computational methods. Modern chiral stationary phases are discussed with particular focus on those that are commercially available and broadly used. It is attempted to provide the reader with vivid images of molecular recognition mechanisms of selected chiral selector-selectand pairs on basis of solid-state X-ray crystal structures and simulated computer models, respectively. Such snapshot images illustrated in this communication unfortunately cannot account for the molecular dynamics of the real world, but are supposed to be helpful for the understanding. The exploding number of papers about applications of various chiral stationary phases in numerous fields of enantiomer separations is not covered systematically.

Analytical characterization of chiral drug-protein interactions: comparison between the optical biosensor (surface plasmon resonance) assay and the HPLC perturbation method

Two modern, fundamentally different methods were used for a detailed investigation of enantioselective drug-protein interactions, a surface plasmon resonance (SPR)-based Biacore 2000 biosensor assay and the previously validated HPLC perturbation method (HPLC-PM). This is the first time SPR has been used for this purpose. The fundamental features of the two methods were investigated, and the consequences for operation and data evaluation were addressed. With HPLC-PM, chiral data could be obtained directly from the racemic mixture, whereas a separate analysis of each pure enantiomer was required to obtain chiral data with SPR. It was shown that if chirality is not attributed in the SPR analysis, misleading average racemic binding constants will be obtained. Both drug and protein consumption were considerably higher with HPLC-PM. HPLC-PM was found to be best suited for measurements of weak affinity interactions, whereas the SPR method was best for strong interactions. With both methods, the presence of DMSO in the samples severely affected the interactions, introducing errors. The binding of the beta-blockers alprenolol and propranolol to Cel7a cellulase was used as a model system. These methods gave results that agreed quite well qualitatively, but considerable quantitative deviations were sometimes obtained.

pH dependency of ligand binding to cellobiohydrolase 1 (Cel7A)

The affinity and enantioselectivity have been determined for designed propranolol derivatives as ligands for Cel7A by capillary electrophoresis (CE) at pH 7.0. These results have been compared to measurements at pH 5.0. In agreement with previous studies, the affinity increased at the higher pH. However, the affinity was not as dependent of the ligand structure at pH 7.0 as at pH 5.0, and the selectivity was generally decreased. Instead, at pH 7.0, the changes in binding were mainly dependent on the presence of additional dihydroxyl groups, indicating an increased importance of the electrostatic interactions. To evaluate the pH dependent variations in binding, changes in both the ligand and in the enzyme had to be taken into account. To ensure that the ligands had the same charge in all measurements, pKa-values of all compounds were determined. The ligand-protein interaction has also been studied by inhibition experiments at both pHs to evaluate the specific binding to the active site when competing with the substrate p-nitrophenyl lactoside (pNPL). With support of docking computations we propose a hypothesis on the effect of the ligand structure and pH dependency of the binding and selectivity of amino alcohols to Cel7A.

Analysis of the Surfaces of Wood Tissues and Pulp Fibers Using Carbohydrate-Binding Modules Specific for Crystalline Cellulose and Mannan

Carbohydrate binding modules (CBMs) are noncatalytic substrate binding domains of many enzymes involved in carbohydrate metabolism. Here we used fluorescent labeled recombinant CBMs specific for crystalline cellulose (CBM1(HjCel7A)) and mannans (CBM27(TmMan5) and CBM35(CjMan5C)) to analyze the complex surfaces of wood tissues and pulp fibers. The crystalline cellulose CBM1(HjCel7A) was found as a reliable marker of both bacterially produced and plant G-layer cellulose, and labeling of spruce pulp fibers with CBM1(HjCel7A) revealed a signal that increased with degree of fiber damage. The mannan-specific CBM27(TmMan5) and CBM35(CjMan5C) CBMs were found to be more specific reagents than a monoclonal antibody specific for (1-->4)-beta-mannan/galacto-(1-->4)-beta-mannan for mapping carbohydrates on native substrates. We have developed a quantitative fluorometric method for analysis of crystalline cellulose accumulation on fiber surfaces and shown a quantitative difference in crystalline cellulose binding sites in differently processed pulp fibers. Our results indicated that CBMs provide useful, novel tools for monitoring changes in carbohydrate content of nonuniform substrate surfaces, for example, during wood or pulping processes and possibly fiber biosynthesis.

Rational and efficient geometric definition of pharmacophores is essential for the patent process

The geometric description of pharmacophores suffers from approximations. No consensus has been clearly established, despite the increasing interest in using pharmacophores in drug design and in patent applications. We therefore propose an original definition of a pharmacophore using spherical coordinates. These coordinates give a precise description of each point using three parameters: distance to a geometric origin and two angles. If necessary, these parameters can be easily and rapidly converted to cartesian coordinates. Our method can guarantee, to the patent applicant, the safe protection of his intellectual property by both improving markedly the readability of a pharmacophore definition and bringing, to the person who is skilled in the art, enough information to understand easily the essence of the invention.

New propranolol analogues: binding and chiral discrimination by cellobiohydrolase Cel7A

Novel propranolol analogues have been designed and synthesised and their enantioselective binding to the cellulose degrading enzyme, Cel7A, has been evaluated. Affinity and enantioselectivity have been determined by capillary electrophoresis experiments. Ligands with significantly improved affinity and selectivity have been obtained and an analysis of the results has led to insights concerning the relation between the changes in ligand structure and selectivity as well as affinity to the protein.

Recent developments on cellulases and carbohydrate-binding modules with cellulose affinity

This review concerns basic research on cellulases and cellulose-specific carbohydrate-binding modules (CBMs). As a background, glycosyl hydrolases are also briefly reviewed. The nomenclature of cellulases and CBMs is discussed. The main cellulase-producing organisms and their cellulases are described. Synergy, enantioseparation, cellulases in plants, cellulosomes, cellulases and CBMs as analytical tools and cellulase-like enzymes are also briefly reviewed.

Separation of drug enantiomers by liquid chromatography and capillary electrophoresis, using immobilized proteins as chiral selectors

Proteins display interesting chiral discrimination properties owing to multiple possibilities of intermolecular interactions with chiral compounds. This review deals with proteins which have been used as immobilized chiral selectors for the enantioseparation of drugs in liquid chromatography and capillary electrophoresis. The main procedures allowing the immobilization of proteins onto matrices, such as silica and zirconia particles, membranes and capillaries are first presented. Then the factors affecting the enantioseparation of drugs in liquid chromatography, using various protein-based chiral stationary phases (CSPs), are reviewed and discussed. Last, chiral separations already achieved using immobilized protein selectors in affinity capillary electrochromatography (ACEC) are presented and compared in terms of efficiency, stability and reproducibility.

Engineering the Exo-loop of Trichoderma reesei Cellobiohydrolase, Cel7A. A comparison with Phanerochaete chrysosporium Cel7D

The exo-loop of Trichoderma reesei cellobiohydrolase Cel7A forms the roof of the active site tunnel at the catalytic centre. Mutants were designed to study the role of this loop in crystalline cellulose degradation. A hydrogen bond to substrate made by a tyrosine at the tip of the loop was removed by the Y247F mutation. The mobility of the loop was reduced by introducing a new disulphide bridge in the mutant D241C/D249C. The tip of the loop was deleted in mutant Delta(G245-Y252). No major structural disturbances were observed in the mutant enzymes, nor was the thermostability of the enzyme affected by the mutations. The Y247F mutation caused a slight k(cat) reduction on 4-nitrophenyl lactoside, but only a small effect on cellulose hydrolysis. Deletion of the tip of the loop increased both k(cat) and K(M) and gave reduced product inhibition. Increased activity was observed on amorphous cellulose, while only half the original activity remained on crystalline cellulose. Stabilisation of the exo-loop by the disulphide bridge enhanced the activity on both amorphous and crystalline cellulose. The ratio Glc(2)/(Glc(3)+Glc(1)) released from cellulose, which is indicative of processive action, was highest with Tr Cel7A wild-type enzyme and smallest with the deletion mutant on both substrates. Based on these data it seems that the exo-loop of Tr Cel7A has evolved to facilitate processive crystalline cellulose degradation, which does not require significant conformational changes of this loop.

Stereoselective chromatography of cardiovascular drugs: an update

This review reports the latest achievements in chromatographic enantioseparations of various classes of cardiovascular drugs and selected applications of these methods in pharmaceutical and clinical analysis. The use of these drugs as test compounds for new chiral stationary phases and different parameters of chromatographic processes is also presented.