A β-glucosidase from Sclerotinia sclerotiorum

The filamentous fungus Sclerotinia sclerotiorum, grown on a xylose medium, was found to excrete one β-glucosidase (β-glu x). The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, anion-exchange chromatography, and high-performance liquid chromatography (HPLC) gel filtration chromatography. Its molecular mass was estimated to be 130 kDa by HPLC gel filtration and 60 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis, suggesting that β-glu x may be a homodimer. For p-nitrophenyl β-d-glucopyranoside hydrolysis, apparent K _m and V _max values were found to be 0.09 mM and 193 U/mg, respectively, while optimum temperature and pH were 55–60°C and pH 5.0, respectively. β-Glu x was strongly inhibited by Fe²⁺ and activated about 35% by Ca²⁺. β-Glu x possesses strong transglucosylation activity in comparison with commercially available β-glucosidases. The production rate of total glucooligosaccharides (GOSs) from 30% cellobiose at 50°C and pH 5.0 for 6 h with 0.6 U/mL of enzyme preparation was 80 g/L. It reached 105 g/L under the same conditions when using cellobiose at 350 g/L (1.023 M). Finally, GOS structure was determined by mass spectrometry and ¹³C nuclear magnetic resonance spectroscopy.     

Convolution semigroups and central limit theorem associated with a dual convolution structure

We consider hypergroups associated with Jacobi functions ⁽⁾ (x), (–1/2). We prove the existence of a dual convolution structure on [0,+[i(]0,s ₀]{{) =++1,s ₀=min(,–+1). Next we establish a Lévy-Khintchine type formula which permits to characterize the semigroup and the infinitely divisible probabilities associated with this dual convolution, finally we prove a central limit theorem.     

Antichain cutsets

A subset A of an ordered set P is a cutset if each maximal chain of P meets A; if, in addition, A is an antichain call it an antichain cutset. Our principal result is a characterization, by means of a forbidden configuration, of those finite ordered sets, which can be expressed as the union of antichain cutsets.     

A beta-glucosidase from Sclerotinia sclerotiorum: biochemical characterization and use in oligosaccharide synthesis

The filamentous fungus Sclerotinia sclerotiorum, grown on a xylose medium, was found to excrete one beta-glucosidase (beta-glu x). The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, anion-exchange chromatography, and high-performance liquid chromatography (HPLC) gel filtration chromatography. Its molecular mass was estimated to be 130 kDa by HPLC gel filtration and 60 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis, suggesting that beta-glu x may be a homodimer. For p-nitrophenyl beta-d-glucopyranoside hydrolysis, apparent Km and Vmax values were found to be 0.09 mM and 193 U/mg, respectively, while optimum temperature and pH were 55-60 degrees C and pH 5.0, respectively. beta-Glu x was strongly inhibited by Fe2+ and activated about 35% by Ca2+. beta-Glu x possesses strong transglucosylation activity in comparison with commercially available beta-glucosidases. The production rate of total glucooligosaccharides (GOSs) from 30% cellobiose at 50 degrees C and pH 5.0 for 6 h with 0.6 U/mL of enzyme preparation was 80 g/L. It reached 105 g/L under the same conditions when using cellobiose at 350 g/L (1.023 M). Finally, GOS structure was determined by mass spectrometry and 3C nuclear magnetic resonance spectroscopy.     

Purification and characterization of two low molecular weight endoglucanases produced by Penicillium occitanis mutant pol 6

Two endoglucanases (EGs), EG A and EG B, were purified to homogeneity from Penicillium occitanis mutant Pol 6 culture medium. The molecular weights of EG A and EG B were 31,000 and 28,000 kDa, respectively. The pI was about 3 for EG A and 7.5 for EG B. Optimal activity was obtained at pH 3.5 for both endoglucanases. Optimal temperature for enzyme activity was 60 degrees C for EG A and 50 degrees C for EG B. EG A was thermostable at 60 degrees C and remained active after 1 h at 70 degrees C. EGs hydrolyzed carboxymethylcellulose, phosphoric acid swollen cellulose, and beta-glucan efficiently, whereas microcrystalline cellulose (Avicel) and laminarin were poorly hydrolyzed. Only EG B showed xylanase activity. Furthermore, these EGs were insensitive to the action of glucose and cellobiose but were inhibited by the divalent cations Hg2+, Co2+, and Mn2+.     

MS Analysis and Molecular Characterization of Botrytis cinerea Protease Prot-2. Use in Bioactive Peptides Production

Prot-2 protease previously purified to homogeneity from Botrytis cinerea showed potentiality to be used in detergency and for production of bioactive peptides. To extend the characterization of Prot-2 protease, antifungal and antibacterial assays were performed in vitro using protein hydrolysates prepared from muscle of mackerel (Scomber scomborus) treated with this enzyme. The most active hydrolysate (degree of hydrolysis of 8 %) exhibited inhibition effect towards bacteria and phytopathogenic fungi, demonstrating that Prot-2 proteolysis generated bioactive peptides. Biochemical and molecular characterization of the purified Prot-2, by SDS-PAGE/Tryptic in gel-digestion and LC-MS/MS analysis, was investigated. The peptide amino acid sequence alignment search in database revealed a moderate homology between the determined amino acid sequence of Prot-2 protease and the known fungal trypsin/chymotrypsin in particular from Glomerella, Metarhizium and Streptomyces. From peptide sequence data obtained by mass spectrometry and sequences homologies, primers were defined and a cDNA fragment of 786 bp was amplified by RT-PCR. The cDNA nucleotide sequence analysis revealed an open reading frame coding for 262 amino acid residues. The deduced amino acid sequence of Prot-2 showed moderate identity with trypsin of Glomerella graminicola (74 %) and with chymotrypsin from Metarhizium anisopliae (71 %). Prot-2 exhibited a Ser protease homology and showed in addition the specific His motif of trypsin/chymotrypsin family.     

Scheduling tasks with communication delays on parallel processors

LetP={v ₁,...,v _n } be a set ofn jobs to be executed on a set ofm identical machines. In many instances of scheduling problems, if a jobv _i has to be executed before the jobv _j and both jobs are to be executed on different machines, some sort of information exchange has to take place between the machines executing them. The time it takes for this exchange of information is called a communication delay.In this paper we give anO(n) algorithm to find an optimal scheduling with communication delays when the number of machines is not limited and the precedence constraints on the jobs form a tree.     

Tandem diazonium salt electroreduction and click chemistry as a novel, efficient route for grafting macromolecules to gold surface

Bis-alkynylated oligoethyleneglycol (OEG) and a monopropargyl-functionalized perfluorinated ethylene glycol (FEG) were clicked to azide-functionalized gold surface (Au–N₃) at room temperature via the well known 1,3 cycloaddition click chemical reaction. The Au–N₃ substrate was obtained by nucleophilic attack of NaN₃ on gold substrates modified by the electrochemical reduction of the , ⁺N₂–C₆H₄–CH₂Br diazonium salt. This electrochemical process yields aryl layer-modified gold of the type Au–C₆H₄–CH₂Br (hereafter Au–Br). The untreated and modified gold plates were examined by XPS, PMIRRAS and contact angle measurements. XPS brought evidence for electrografting aryl layers by the detection of Br3d; azide functionalization by the increase of the N/Br atomic ratio; and click reaction of OEG with Au–N₃ by the increase of O/N ratio. In addition, the perfluorinated plate (Au-FEG) exhibited F1s and characteristic C1s peaks from -(CF₂)₇- chain and terminal CF₃. Infra red spectroscopy (PMIRRAS) evidenced (i) grafting N₃ to Au–Br; (ii) characteristic stretching bands, from ethylene glycol units, C–O–C (1100–1300 cm⁻¹); CF₂ (1000–1100 cm⁻¹) and CF₃ (1100–1350 cm⁻¹) from FEG grafts; and (iii) suppression of alkynyl bands from OEG and FEG after surface click chemistry. More importantly, PMIRRAS results support an important bridging of the bispropargyl oligoethylene glycol at the gold surface. Water drop contact angles were found to be 48.7° and 83.0° for Au-OEG and Au-FEG, respectively, therefore highlighting the control over the hydrophilic/hydrophobic character of the clicked substrate.This work shows that clicking macromolecules to grafted, diazonium salt-derived aryl layers is a novel, simple and valuable approach for designing robust, functional surface organic coatings.     

Logistic chaotic maps for binary numbers generations

Two pseudorandom binary sequence generators, based on logistic chaotic maps intended for stream cipher applications, are proposed. The first is based on a single one-dimensional logistic map which exhibits random, noise-like properties at given certain parameter values, and the second is based on a combination of two logistic maps. The encryption step proposed in both algorithms consists of a simple bitwise XOR operation of the plaintext binary sequence with the keystream binary sequence to produce the ciphertext binary sequence. A threshold function is applied to convert the floating-point iterates into binary form. Experimental results show that the produced sequences possess high linear complexity and very good statistical properties. The systems are put forward for security evaluation by the cryptographic committees.     

On the definition of the stress tensor in granular media

This paper investigates the definition of the stress tensor within a granular assembly, when inertial effects are likely to occur. It is shown that the stress tensor can be expressed as a sum of two terms. A first term corresponds to the standard definition of the stress, according to the Love–Weber formula; this term is related to the contact forces existing within adjoining particles. A second term accounts for dynamic effects related to rotation velocities and accelerations of the particles. These results are checked from discrete numerical simulations in order to examine in which context the contribution of inertial effects should not be omitted. With this aim, the simulation of a granular specimen collapse and then a silo discharge is considered.