SELECTIVE AND CONVENIENT OXIDATION OF THIOLS TO DISULFIDES USING n-BUTYLTRIPHENYLPHOSPHONIUM DICHROMATE (Bu n PPh3)2Cr2O7 IN SOLUTION,UNDER SOLVENT-FREE CONDITIONS AND MICROWAVE IRRADIATION

A variety of aliphatic, aromatic, and heteroaromatic thiols were rapidly and cleanly converted to their corresponding disulfides in excellent yields using n-butyltriphenylphosphonium dichromate (BTPPDC) in acetonitrile solution under solvent-free conditions and microwave irradiation. Selective oxidation of thiols in the presence of other oxidizable functional groups, such as alcohol and sulfide, is a noteworthy advantage of this method.     

Effect of Additives on Freeze-Drying and Storage of Yarrowia lipolytica Lipase

The extracellular lipase of Yarrowia lipolytica presents numerous potentialities for biotechnological applications. This work describes the development and storage of powders obtained from supernatants containing Y. lipolytica lipase by freeze-drying as downstream process that is important in obtaining a stable lipase powder with high enzymatic activity. Lipase was produced by Y. lipolytica U6 mutant strain in 20-L bioreactor. Non-concentrated cell-free culture supernatant samples were supplemented with different concentrations (0.5?C1?%) of maltodextrin and glycerol as additives to freeze-drying. Effects of additives, temperature, pH, and storage time on lipase powders were determined. After addition of additives, freeze-drying yield increased 3.5-fold compared to supernatant without additive. Maltodextrin with 0.5?% concentration gave the best protection of lipase during dehydration treatment and its freeze-drying yield (77?%) is better than other formulations. Lipase powders were stored at 4 and 25?°C for 46?weeks without loss of lipase activity. A common impediment to the production of commercial enzyme is their low-stability aqueous solutions. The present study shows that freeze-dried lipase powders of Y. lipolytica have good stability for storage and various applications.     

Sonocatalytic epoxidation of alkenes by vanadium-containing polyphosphomolybdate immobilized on multi-wall carbon nanotubes

A Keggin type polyoxometalate (POM) has been immobilized in the unique network structure of multi-wall carbon nanotubes (CNTs). The vanadium-containing polyphosphomolybdate (PVMo) supported on CNTs, which was prepared by a one-step solid-state reaction, was characterized by FT-IR, XRD, SEM and elemental analyses. These uniform nanoparticles have an average size 20–30 nm. Furthermore, due to the chemical interaction between PVMo and carboxylic acid groups, PVMo nanoparticles were successfully immobilized on the CNTs. Moreover, the obtained composite was found as an efficient catalyst for oxidation of hydrocarbons under reflux and ultrasonic irradiation (US) conditions.     

Functional Mutations in and Characterization of VHH Against Helicobacter pylori Urease

Manipulation of clinically significant antibodies can effectively improve the processes of diagnosis and treatment. Affinity maturation process has a significant role in improvement of antibodies efficiency. Error-prone PCR technique is one of the proposed methods for improvement of the affinity of antibodies. In the present research, a method was applied to camel heavy-chain antibody (VHH, nanobody) raised against UreC subunit of urease enzyme from Helicobacter pylori. This VHH was used as a starting molecule to construct a highly diversified phage displayed VHH library. The constructed library of nanobody mutants was subjected to several rounds of panning against UreC antigen. High-affinity mutant was selected. Our VHH (HMR23) showed 1.5-fold higher binding activity than the parental VHH. In addition, the mutant VHH presented a better performance in inhibition of urease activity at low concentrations retaining its specificity and thermal stability.     

Efficient and Eco‐friendly Syntheses of 1,5‐Benzothiazepines and 1,5‐Benzodiazepines Catalyzed by [Hmim][NO3] under Mild Conditions

This article presents a synthetic method and reaction mechanism of the 1,5‐benzothiazepines and 1,5‐benzodiazepines derivatives. In this research, 36 thiazepines and diazepines (mostly new) with a new method have been prepared and their structures have been characterized by spectroscopic methods. Crystal structures of a new thiazepine and diazepine (seven‐membered rings) have also been determined and compared with thiazine (six‐membered ring). In this method, N‐methylimidazolium nitrate [Hmim][NO₃] has been used as a catalyst that acts as an environmental friendly system.     

Solvent-Free,Cross-Aldol Condensation Reaction Using Silica-Supported,Phosphorus-Containing Reagents Leading to α,α′-Bis(arylidene)cycloalkanones

This article describes an efficient, simple, and clean method for the synthesis of α,α′-bis(arylidene, furylidene and cinnamylidene)cycloalkanones under solvent-free conditions. The cross-aldol condensation of cycloalkanones with aldehydes in the presence of silica-supported phosphorus pentoxide (P₂O₅/SiO₂) or silicaphosphinoxide (silphox, [POCl_3-n(SiO₂)_n]) as heterogeneous reagents produces the title compounds in good to excellent yields.     

Selective oxidation of alkenes using [bmim]5[PW11ZnO39]·3H2O hybrid catalyst

The catalytic activity of [bmim]₅[PW₁₁ZnO₃₉]·3H₂O as a hybrid catalyst was studied in the oxidation of various alkenes in acetonitrile, using hydrogen peroxide as oxygen source. The effect of reaction parameters such as type of solvent and oxidant, amount of catalyst and oxidant, and temperature was also investigated. From our results, [bmim]₅[PW₁₁ZnO₃₉]·3H₂O hybrid catalyst gave higher yields and selectivity in the oxidation of alkenes and was reused four times without loss of its catalytic activity.     

Multi-wall carbon nanotube supported manganese(III) porphyrin: an efficient and reusable catalyst for oxidation of 2-imidazolines with sodium periodate

The oxidation of 2-substituted imidazolines with sodium periodate catalyzed by tetrakis(p-aminophenyl)-porphyrinatomanganese(III) chloride, [Mn(TNH₂PP)Cl], supported on functionalized multi-wall carbon nanotubes is reported. A wide variety of 2-imidazolines were efficiently converted to their corresponding imidazoles by this catalytic system. When the same reaction was subjected to ultrasonic irradiation, the reaction times were reduced significantly and the product yields were increased. This catalyst could be reused several times without significant loss of activity. The effects of reaction parameters such catalyst amount, choice of solvent, and the effects of ultrasonic irradiation on the catalytic activity have been investigated.