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See detailCrystal Structure of the Extended-Spectrum β -Lactamase PER-2 and Insights into the Role of Specific Residues in the Interaction with β -Lactams and β -Lactamase Inhibitors
Ruggiero, Melina; Kerff, Frédéric ULiege; Herman, Raphaël ULiege et al

in Antimicrobial Agents and Chemotherapy (2014), 58(10), 5994-6002

PER-2 belongs to a small (7 members to date) group of extended-spectrum beta-lactamases. It has 88% amino acid identity with PER-1 and both display high catalytic efficiencies toward most beta-lactams. In ... [more ▼]

PER-2 belongs to a small (7 members to date) group of extended-spectrum beta-lactamases. It has 88% amino acid identity with PER-1 and both display high catalytic efficiencies toward most beta-lactams. In this study, we determined the X-ray structure of PER-2 at 2.20 A and evaluated the possible role of several residues in the structure and activity toward beta-lactams and mechanism-based inhibitors. PER-2 is defined by the presence of a singular trans bond between residues 166 to 167, which generates an inverted Omega loop, an expanded fold of this domain that results in a wide active site cavity that allows for efficient hydrolysis of antibiotics like the oxyimino-cephalosporins, and a series of exclusive interactions between residues not frequently involved in the stabilization of the active site in other class A beta-lactamases. PER beta-lactamases might be included within a cluster of evolutionarily related enzymes harboring the conserved residues Asp136 and Asn179. Other signature residues that define these enzymes seem to be Gln69, Arg220, Thr237, and probably Arg/Lys240A ("A" indicates an insertion according to Ambler's scheme for residue numbering in PER beta-lactamases), with structurally important roles in the stabilization of the active site and proper orientation of catalytic water molecules, among others. We propose, supported by simulated models of PER-2 in combination with different beta-lactams, the presence of a hydrogen-bond network connecting Ser70-Gln69-water-Thr237-Arg220 that might be important for the proper activity and inhibition of the enzyme. Therefore, we expect that mutations occurring in these positions will have impacts on the overall hydrolytic behavior. [less ▲]

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See detailCrystal structure of the IMP-1 metallo beta-lactamase from Pseudomonas aeruginosa and its complex with a mercaptocarboxylate inhibitor: binding determinants of a potent, broad-spectrum inhibitor.
Concha, N. O.; Janson, C. A.; Rowling, P. et al

in Biochemistry (2000), 39(15), 4288-98

Metallo beta-lactamase enzymes confer antibiotic resistance to bacteria by catalyzing the hydrolysis of beta-lactam antibiotics. This relatively new form of resistance is spreading unchallenged as there ... [more ▼]

Metallo beta-lactamase enzymes confer antibiotic resistance to bacteria by catalyzing the hydrolysis of beta-lactam antibiotics. This relatively new form of resistance is spreading unchallenged as there is a current lack of potent and selective inhibitors of metallo beta-lactamases. Reported here are the crystal structures of the native IMP-1 metallo beta-lactamase from Pseudomonas aeruginosa and its complex with a mercaptocarboxylate inhibitor, 2-[5-(1-tetrazolylmethyl)thien-3-yl]-N-[2-(mercaptomethyl)-4 -(phenylb utyrylglycine)]. The structures were determined by molecular replacement, and refined to 3.1 A (native) and 2.0 A (complex) resolution. Binding of the inhibitor in the active site induces a conformational change that results in closing of the flap and transforms the active site groove into a tunnel-shaped cavity enclosing 83% of the solvent accessible surface area of the inhibitor. The inhibitor binds in the active site through interactions with residues that are conserved among metallo beta-lactamases; the inhibitor's carboxylate group interacts with Lys161, and the main chain amide nitrogen of Asn167. In the "oxyanion hole", the amide carbonyl oxygen of the inhibitor interacts through a water molecule with the side chain of Asn167, the inhibitor's thiolate bridges the two Zn(II) ions in the active site displacing the bridging water, and the phenylbutyryl side chain binds in a hydrophobic pocket (S1) at the base of the flap. The flap is displaced 2.9 A compared to the unbound structure, allowing Trp28 to interact edge-to-face with the inhibitor's thiophene ring. The similarities between this inhibitor and the beta-lactam substrates suggest a mode of substrate binding and the role of the conserved residues in the active site. It appears that the metallo beta-lactamases bind their substrates by establishing a subset of binding interactions near the catalytic center with conserved characteristic chemical groups of the beta-lactam substrates. These interactions are complemented by additional nonspecific binding between the more variable groups in the substrates and the flexible flap. This unique mode of binding of the mercaptocarboxylate inhibitor in the enzyme active site provides a binding model for metallo beta-lactamase inhibition with utility for future drug design. [less ▲]

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See detailCrystal Structure of the Lysozyme from Bacteriophage Lambda and its Relationship with V and C-type Lysozymes
Evrard, Christine ULiege; Fastrez, Jacques; Declercq, Jean-Paul

in Journal of Molecular Biology (1998), 276

Like other lysozymes, the bacteriophage lambda lysozyme is involved in the digestion of bacterial walls. This enzyme is remarkable in that its mechanism of action is different from the classical lysozyme ... [more ▼]

Like other lysozymes, the bacteriophage lambda lysozyme is involved in the digestion of bacterial walls. This enzyme is remarkable in that its mechanism of action is different from the classical lysozyme's mechanism. From the point of view of protein evolution, it shows features of lysozymes from different classes. The crystal structure of the enzyme in which all tryptophan residues have been replaced by aza-tryptophan has been solved by X-ray crystallography at 2.3 Å using a combination of multiple isomorphous replacement, non-crystallographic symmetry averaging and density modification techniques. There are three molecules in the asymmetric unit. The characteristic structural elements of lysozymes are conserved: each molecule is organized in two domains connected by a helix and the essential catalytic residue (Glu19) is located in the depth of a cleft between the two domains. This cleft shows an open conformation in two of the independent molecules, while access to the cavity is much more restricted in the last one. A structural alignment with T4 lysozyme and hen egg white lysozyme allows us to superpose about 60 Cα atoms with a rms distance close to 2 Å. The best alignments concern the helix preceding the catalytic residue, some parts of the beta sheets and the helix joining the two domains. The results of sequence alignments with the V and C lysozymes, in which weak local similarities had been detected, are compared with the structural results. [less ▲]

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See detailCrystal structure of the Mycobacterium fortuitum class A beta-lactamase: structural basis for broad substrate specificity.
Sauvage, Eric ULiege; Fonze, Eveline; Quinting, Birgit et al

in Antimicrobial Agents and Chemotherapy (2006), 50(7), 2516-21

beta-Lactamases are the main cause of bacterial resistance to penicillins and cephalosporins. Class A beta-lactamases, the largest group of beta-lactamases, have been found in many bacterial strains ... [more ▼]

beta-Lactamases are the main cause of bacterial resistance to penicillins and cephalosporins. Class A beta-lactamases, the largest group of beta-lactamases, have been found in many bacterial strains, including mycobacteria, for which no beta-lactamase structure has been previously reported. The crystal structure of the class A beta-lactamase from Mycobacterium fortuitum (MFO) has been solved at 2.13-A resolution. The enzyme is a chromosomally encoded broad-spectrum beta-lactamase with low specific activity on cefotaxime. Specific features of the active site of the class A beta-lactamase from M. fortuitum are consistent with its specificity profile. Arg278 and Ser237 favor cephalosporinase activity and could explain its broad substrate activity. The MFO active site presents similarities with the CTX-M type extended-spectrum beta-lactamases but lacks a specific feature of these enzymes, the VNYN motif (residues 103 to 106), which confers on CTX-M-type extended-spectrum beta-lactamases a more efficient cefotaximase activity. [less ▲]

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See detailCrystal structure of the sensor domain of the BlaR penicillin receptor from Bacillus licheniformis
Kerff, Frédéric ULiege; Charlier, Paulette ULiege; Colombo, Maria Louisa et al

in Biochemistry (2003), 42(44), 12835-12843

As in several staphylococci, the synthesis of the Bacillus licheniformis 749/I beta-lactamase is an inducible phenomenon regulated by a signal-transducing membrane protein BlaR. The C-terminal domain of ... [more ▼]

As in several staphylococci, the synthesis of the Bacillus licheniformis 749/I beta-lactamase is an inducible phenomenon regulated by a signal-transducing membrane protein BlaR. The C-terminal domain of this multimodular protein is an extracellular domain which specifically recognizes beta-lactam antibiotics. When it binds a beta-lactam, a signal is transmitted by the transmembrane region to the intracellular loops. In response, the hydrolytic activity of the BlaR large cytoplasmic L3 loop is induced, and a cascade of reactions is generated, leading to the transcription of the beta-lactamase gene. Here, we describe the crystal structure of the extracellular penicillin-receptor domain of BlaR (residues 346-601) at 2.5 Angstrom resolution in order to understand why this domain, whose folding is very similar to that of class D beta-lactamases, behaves as a highly sensitive penicillin-binding protein rather than a beta-lactamase. Two residues of the BlaR C-terminal domain, Thr452 and Thr542, modify the hydrophobic characteristic of the class D beta-lactamase active site. Both residues seem to be in part responsible for the lack of beta-lactamase activity of the BlaR protein due to the stability of the acyl-enzyme. Although further experimental data are needed to fully understand the transmembrane induction process, the comparison of the BlaR sensor domain structure with those of class D beta-lactamase complexes and penicillin-binding proteins provides interesting elements to hypothesize on possible signal transmission mechanisms. [less ▲]

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See detailThe crystal structure of the β-lactamase of Streptomyces albus G at 0.3 nm resolution
Dideberg, Otto; Charlier, Paulette ULiege; Wery, Jean-Paul et al

in Biochemical Journal (1987), 245(3), 911-913

The crystal structure of the beta-lactamase of Streptomyces albus G has been solved at 0.3 nm resolution by X-ray-diffraction methods. The enzyme is a typical two-domain protein. One domain consists of ... [more ▼]

The crystal structure of the beta-lactamase of Streptomyces albus G has been solved at 0.3 nm resolution by X-ray-diffraction methods. The enzyme is a typical two-domain protein. One domain consists of five alpha-helices, and the other is five-stranded beta-sheet with alpha-helices on both sides of the sheet. The active-site serine residue (Ser-48) is within a cleft located between the two domains. [less ▲]

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See detailThe crystal structure of triosephosphate isomerase (TIM) from Thermotoga maritima: a comparative thermostability structural analysis of ten different TIM structures
Maes, Dominique; Zeelen, Johan P.; Thanki, Narmada et al

in Proteins (1999), 37(3), 441-53

The molecular mechanisms that evolution has been employing to adapt to environmental temperatures are poorly understood. To gain some further insight into this subject we solved the crystal structure of ... [more ▼]

The molecular mechanisms that evolution has been employing to adapt to environmental temperatures are poorly understood. To gain some further insight into this subject we solved the crystal structure of triosephosphate isomerase (TIM) from the hyperthermophilic bacterium Thermotoga maritima (TmTIM). The enzyme is a tetramer, assembled as a dimer of dimers, suggesting that the tetrameric wild-type phosphoglycerate kinase PGK-TIM fusion protein consists of a core of two TIM dimers covalently linked to 4 PGK units. The crystal structure of TmTIM represents the most thermostable TIM presently known in its 3D-structure. It adds to a series of nine known TIM structures from a wide variety of organisms, spanning the range from psychrophiles to hyperthermophiles. Several properties believed to be involved in the adaptation to different temperatures were calculated and compared for all ten structures. No sequence preferences, correlated with thermal stability, were apparent from the amino acid composition or from the analysis of the loops and secondary structure elements of the ten TIMs. A common feature for both psychrophilic and T. maritima TIM is the large number of salt bridges compared with the number found in mesophilic TIMs. In the two thermophilic TIMs, the highest amount of accessible hydrophobic surface is buried during the folding and assembly process. [less ▲]

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See detailCrystal structure of trisodium iron diphosphate, Na2.88Fe(PO4)(2), a synthetic phosphate with hannayite-type heteropolyhedral chains
Hatert, Frédéric ULiege

in Zeitschrift für Kristallographie. New Crystal Structures (2007), 222(1), 6-8

FeNa2.88O8P2, triclinic, P (1) over bar (no. 2), a 5.3141(6) b = 8.5853(9) angstrom, c = 8.7859(8) angstrom, alpha = 114.429(9)degrees, beta = 92.327(9)degrees, gamma = 106.08(1)degrees, V = 345.1 ... [more ▼]

FeNa2.88O8P2, triclinic, P (1) over bar (no. 2), a 5.3141(6) b = 8.5853(9) angstrom, c = 8.7859(8) angstrom, alpha = 114.429(9)degrees, beta = 92.327(9)degrees, gamma = 106.08(1)degrees, V = 345.1 angstrom(3),Z = 2, Rgt(F) = 0.028, wR(ref)(F-2) = 0.087, T = 293 K. [less ▲]

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See detailCrystal structures of complexes of bacterial DD-peptidases with peptidoglycan-mimetic ligands: the substrate specificity puzzle.
Sauvage, Eric ULiege; Powell, Ailsa J; Heilemann, Jason et al

in Journal of Molecular Biology (2008), 381(2), 383-93

The X-ray crystal structures of covalent complexes of the Actinomadura R39 dd-peptidase and Escherichia coli penicillin-binding protein (PBP) 5 with beta-lactams bearing peptidoglycan-mimetic side chains ... [more ▼]

The X-ray crystal structures of covalent complexes of the Actinomadura R39 dd-peptidase and Escherichia coli penicillin-binding protein (PBP) 5 with beta-lactams bearing peptidoglycan-mimetic side chains have been determined. The structure of the hydrolysis product of an analogous peptide bound noncovalently to the former enzyme has also been obtained. The R39 DD-peptidase structures reveal the presence of a specific binding site for the D-alpha-aminopimelyl side chain, characteristic of the stem peptide of Actinomadura R39. This binding site features a hydrophobic cleft for the pimelyl methylene groups and strong hydrogen bonding to the polar terminus. Both of these active site elements are provided by amino acid side chains from two separate domains of the protein. In contrast, no clear electron density corresponding to the terminus of the peptidoglycan-mimetic side chains is present when these beta-lactams are covalently bound to PBP5. There is, therefore, no indication of a specific side-chain binding site in this enzyme. These results are in agreement with those from kinetics studies published earlier and support the general prediction made at the time of a direct correlation between kinetics and structural evidence. The essential high-molecular-mass PBPs have demonstrated, to date, no specific reactivity with peptidoglycan-mimetic peptide substrates and beta-lactam inhibitors and, thus, probably do not possess a specific substrate-binding site of the type demonstrated here with the R39 DD-peptidase. This striking deficiency may represent a sophisticated defense mechanism against low-molecular-mass substrate-analogue inhibitors/antibiotics; its discovery should focus new inhibitor design. [less ▲]

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See detailCrystal structures of oxidized and reduced forms of human mitochondrial thioredoxin 2
Smeets, Aude; Evrard, Christine ULiege; Landtmeters, Marie et al

in Protein Science : A Publication of the Protein Society (2005), 14

Mammalian thioredoxin 2 is a mitochondrial isoform of highly evolutionary conserved thioredoxins. Thioredoxins are small ubiquitous protein–disulfide oxidoreductases implicated in a large variety of ... [more ▼]

Mammalian thioredoxin 2 is a mitochondrial isoform of highly evolutionary conserved thioredoxins. Thioredoxins are small ubiquitous protein–disulfide oxidoreductases implicated in a large variety of biological functions. In mammals, thioredoxin 2 is encoded by a nuclear gene and is targeted to mitochondria by a N-terminal mitochondrial presequence. Recently, mitochondrial thioredoxin 2 was shown to interact with components of the mitochondrial respiratory chain and to play a role in the control of mitochondrial membrane potential, regulating mitochondrial apoptosis signaling pathway. Here we report the first crystal structures of a mammalian mitochondrial thioredoxin 2. Crystal forms of reduced and oxidized human thioredoxin 2 are described at 2.0 and 1.8A ˚ resolution. Though the folding is rather similar to that of human cytosolic/nuclear thioredoxin 1, important differences are observed during the transition between the oxidized and the reduced states of human thioredoxin 2, compared with human thioredoxin 1. In spite of the absence of the Cys residue implicated in dimer formation in human thioredoxin 1, dimerization still occurs in the crystal structure of human thioredoxin 2, mainly mediated by hydrophobic contacts, and the dimers are associated to form two-dimensional polymers. Interestingly, the structure of human thioredoxin 2 reveals possible interaction domains with human peroxiredoxin 5, a substrate protein of human thioredoxin 2 in mitochondria. [less ▲]

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See detailCrystal structures of the Bacillus licheniformis BS3 class A beta-lactamase and of the acyl-enzyme adduct formed with cefoxitin
Fonzé, Evelyne; Vanhove, Mac; Dive, Georges ULiege et al

in Biochemistry (2002), 41(6), 1877-1885

The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common ... [more ▼]

The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common and thoroughly studied cause of antibiotic resistance. Although they escape the hydrolytic activity of the prototypical Staphylococcus aureus beta-lactamase, many cephems are good substrates for a large number of beta-lactamases. However, the introduction of a 7alpha-methoxy substituent, as in cefoxitin, extends their antibacterial spectrum to many cephalosporin-resistant Gram-negative bacteria. The 7alphamethoxy group selectively reduces the hydrolytic action of many beta-lactamases without having a significant effect on the affinity for the target enzymes, the membrane penicillin-binding proteins. We report here the crystallographic structures of the BS3 enzyme and its acyl-enzyme adduct with cefoxitin at 1.7 Angstrom resolution. The comparison of the two structures reveals a covalent acyl-enzyme adduct with perturbed active site geometry, involving a different conformation of the Omega-loop that bears the essential catalytic Glu166 residue. This deformation is induced by the cefoxitin side chain whose position is constrained by the presence of the alpha-methoxy group. The hydrolytic water molecule is also removed from the active site by the 7beta-carbonyl of the acyl intermediate. In light of the interactions and steric hindrances in the active site of the structure of the BS3-cefoxitin acyl-enzyme adduct, the crucial role of the conserved Asn132 residue is confirmed and a better understanding of the kinetic results emerges. [less ▲]

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See detailCrystal structures of the psychrophilic a-amylase from Alteromonas haloplanctis in its native form and complexed with an inhibitor
Aghajari, N.; Feller, Georges ULiege; Gerday, Charles ULiege et al

in Protein Science : A Publication of the Protein Society (1998), 7(6), 564-572

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See detailCrystal-field effects on the thermal conductivity of localized spin metallic compounds
Rassili, Ahmed ULiege; Durczewski, K.; Ausloos, Marcel ULiege

in Physical Review. B : Condensed Matter (1998), 58(9), 5665-5671

The influence of the crystal-electric-field (CEF) splitting on the thermal conductivity is calculated on the basis of a two-level system model applicable to intermetallic magnetic compounds. The localized ... [more ▼]

The influence of the crystal-electric-field (CEF) splitting on the thermal conductivity is calculated on the basis of a two-level system model applicable to intermetallic magnetic compounds. The localized spin scattering contribution kappa(s), in a manner similar to the total electronic thermal conductivity kappa(e), shows a larger increase at low and intermediate temperatures as compared to the case iii which-no crystal-electric-field splitting is taken into account. The influence of some theoretical parameters is also discussed. It is shown that the CEF effect enhances the effect of the magnetic scattering potential, and impurity contributions screen such an enhancement at temperatures below the Debye temperature. Other scattering contributions, e.g., electron-phonon and electron impurities, are also taken into account in our calculation. The theory is in quantitative agreement with data on RA1(2) systems taken as test cases, and leads to values of the level splitting in the 50 K range. [less ▲]

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See detailCrystallisation-driven self-assembly of poly(2-isopropyl-2- oxazoline)-block-poly(2-methyl-2-oxazoline) above the LCST
Legros, Camille ULiege; De Pauw-Gillet, Marie-Claire ULiege; Tam, Kam Chiu et al

in Soft Matter (2015)

The solution behaviour in water of a polyoxazoline-type block copolymer, namely poly(2- isopropyl-2-oxazoline)-block-poly(2-methyl-2-oxazoline), denoted as P(iPrOx-b-MeOx), above the lower critical ... [more ▼]

The solution behaviour in water of a polyoxazoline-type block copolymer, namely poly(2- isopropyl-2-oxazoline)-block-poly(2-methyl-2-oxazoline), denoted as P(iPrOx-b-MeOx), above the lower critical solution temperature (LCST) of the PiPrOx block was exploited to induce a temporary or permanent self-assembly. Spherical micelles were first obtained and could be disassembled in a reversible manner when kept for a short period of time (i.e. t < 1h30) above the LCST, and cooled down to room temperature. In contrast, annealing the copolymer solution for more than 1h30 at 65 °C induced the crystallisation of the PiPrOx block, as evidenced by wide angle X-ray scattering (WAXS) experiments. This crystallisationdriven self-assembly phenomenon resulted in different morphologies, including spherical and distorted crystallised micelles and micron-size fibers, their relative proportion varying with annealing time. Formation of micron-size range fiber-like structures might be explained by a re-organization of parent crystallised micelles. The crystal structure, as determined by WAXS, appeared to be identical to that of the PiPrOx homopolymer. [less ▲]

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See detailCrystallization and Gelation Behavior of Low- and High Melting Waxes in Rice Bran Oil: a Case-Study on Berry Wax and Sunflower Wax
Doan, Chi Diem; Tavernier, Iris; Bin Sintang, Mohd Dona et al

in Food Biophysics (2017), 12

Low-melting berry wax (BEW) has proven to be a good oil gelator with a positive contribution to the consistency and flexibility of the structured oil. Nevertheless, the properties of BEWand the ... [more ▼]

Low-melting berry wax (BEW) has proven to be a good oil gelator with a positive contribution to the consistency and flexibility of the structured oil. Nevertheless, the properties of BEWand the corresponding oleogel have not yet been investigated in-depth. In this research, the difference in crystallization and gelling behavior between sunflower wax (SW), a high melting wax, and BEW, a low-melting wax, in rice bran oil (RBO) was investigated. The difference in melting and crystallization temperatures can be explained by the different chemical composition (long-chain wax esters in SWand shortchain fatty acids in BEW). The heterogeneity in crystal habits (unidirectional platelets versus microcrystalline particles) and polymorphism (orthorhombic versus hexagonal) are responsible for the varying gel strength and hardness of the respective SWand BEW-oleogels. The microcrystalline BEW particles aligned and reorganized during 1-month storage at 5 °C, which leaded to an increase in the gel strength and hardness of BEW-oleogel. The gelling property of SW-oleogel however did not significantly differ after 4 weeks at 5 °C, despite of the appearance of spherulitic crystalline clusters. The changes in the physical properties of wax-based oleogels during storage time were further explored using differential scanning calorimetry, polarized light microscope, powder X-ray diffraction and rheology. [less ▲]

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See detailCrystallization and morphologies of waxes in rice bran oil
Diem Doan, Chi; Patel, Ashok R.; Danthine, Sabine ULiege et al

Conference (2016, September)

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See detailCrystallization and polymorphic behavior of enzymatically produced sunflower oil based cocoa butter equivalents
Kadivar, Sheida; De Clercq, Nathalie; Danthine, Sabine ULiege et al

in European Journal of Lipid Science and Technology (2016), 118

A multi-methodological approach was used to study the isothermal crystallization of cocoa butter (CB) in the presence of sunflower oil based cocoa butter equivalents (CBEs). pNMR, DSC, oscillatory ... [more ▼]

A multi-methodological approach was used to study the isothermal crystallization of cocoa butter (CB) in the presence of sunflower oil based cocoa butter equivalents (CBEs). pNMR, DSC, oscillatory rheology, XRD, and PLM were used for this purpose. All the techniques confirmed that at 20°C isothermal crystallization of all the blends is a two-step process with formation of α crystals in the first step and formation of β’ crystals in the second step. The blends with high amount of CBEs contained more high-melting triacylglycerols (TAGs) and diacylglycerol (DAG) in compare with CB acting as seed crystals enhancing the formation of a- crystals in the first crystallization step. Therefore, the induction time of the first crystallization step was inversely related to the amount of CBE. In contrast, the subsequent polymorphic transition was delayed by the presence of the CBE due to their low-melting TAGs. However, adding up to 5% CBE did not change the Foubert’s parameters for isothermal crystallization significantly. All the blends (except 5% HOSO CBE), had a mediated β’ crystallization. Picturing of the microstructure showed that for the CB and the blends up to 50% large microstructures, indicative of the bV polymorph developed during storage. At 100%, a dense network of spherulites was formed at the beginning of the crystallization period, but upon further storage, no large morphological changes were observed. Practical applications: In recent years, the production of CB has been delayed owing to its cultivation difficulty and low yield due to pest attack, while the world cocoa prices have increased with rising demand and higher chocolate consumption. Therefore, there is a need to develop low-priced and appropriate alternatives to CB. Accordingly, in this study two sunflower oil based CBEs were produced with fatty acid mixtures in the presence of immobilized 1,3-regiospecific lipase. The results from this study could help the fats and oils industries to extend their knowledge on the crystallization and polymorphic behavior of two enzymatically produced sunflower oil based CBEs. [less ▲]

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See detailCrystallization and preliminary X-ray analysis of a bacterial psychrophilic enzyme, phosphoglycerate kinase
Mandelman, D.; Bentahir, M.; Feller, Georges ULiege et al

in Acta Crystallographica Section D-Biological Crystallography (2001), 57(Pt 11), 1666-8

The glycolytic enzyme phosphoglycerate kinase (PGK) from the Antarctic microorganism Pseudomonas sp. TACII18 is a cold-adapted enzyme that displays a high specific activity at low temperatures and ... [more ▼]

The glycolytic enzyme phosphoglycerate kinase (PGK) from the Antarctic microorganism Pseudomonas sp. TACII18 is a cold-adapted enzyme that displays a high specific activity at low temperatures and decreased thermostability relative to its mesophilic counterpart. Herein, the preliminary crystallization and structure solution of psychrophilic PGK in its native form and cocrystallized with 3-phosphoglyceric acid (3-PGA) and the ATP analogue adenylyl imidophosphate (AMP-PNP) is reported. The complexed form of PGK crystallized in 2-3 d at 290 K, whereas the native form of the enzyme required 8-12 months. Morphologically, both crystal forms are similar and X-ray diffraction experiments indicate that the crystals are isomorphous. The crystals diffracted to a resolution of 2.0 A and belong to the space group P3(2). with unit-cell parameters a = b = 58.5, c = 85.4 A. [less ▲]

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See detailCrystallization and preliminary X-ray analysis of a new L-aminopeptidase-D-amidase/D-esterase activated by a Gly-Ser peptide bond hydrolysis.
Bompard-Gilles, C; Villeret, V; Fanuel, L et al

in Acta Crystallographica Section D-Biological Crystallography (1999), 55(Pt 3), 699-701

Ochrobactrum anthropi possesses an L-aminopeptidase (DmpA) also able to act as a D-amidase/D-esterase. DmpA (40 kDa) is activated by auto-catalyzed protein splicing liberating an alpha-amino group ... [more ▼]

Ochrobactrum anthropi possesses an L-aminopeptidase (DmpA) also able to act as a D-amidase/D-esterase. DmpA (40 kDa) is activated by auto-catalyzed protein splicing liberating an alpha-amino group presumably used as a general base in the catalytic mechanism. Two crystal forms were obtained at 294 K in 13-16% PEG 2000 mono-methylether at pH 9.0, adding either 0.2 M magnesium chloride or 1 M lithium chloride. Crystals of the first form belong to the space group C2221 and diffract to 3.0 A resolution, whereas crystals of the second form belong to the space group P21212 and diffract to 2.3 A resolution. Initial screening for heavy-atom derivatives on form II crystals, has led to a well substituted Hg derivative. [less ▲]

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