Jawaid Iqbal

Immobilization and stabilization of papain on chelating sepharose: a metal chelate regenerable carrier

A method for immobilization of papain has been selected based on the interaction between its histidine, cysteine and tryptophan residues with the immobilized metal ion (IMI) carrier for maximum binding on a small volume of the carrier. The immobilized papain retained high activity has improved thermal stability and the carrier could be recovered from the spent bound enzyme, to be reused. Reimmobilization of papain on the regenerated matrix was equally effective with the retention of maximum enzyme activity.

Sucrose hydrolysis using invertase immobilized on concanavalin A-sepharose

Abstract The stability and ability of yeast invertase (β- d -fructofuranoside fructohydrolase, EC 3.2.1.26) bound and covalently coupled to concanavalin A-Sepharose continuously to hydrolyse sucrose over long periods has been investigated. The immobilized preparation exhibited high resistance to heat and urea induced denaturation. A small column of the immobilized preparation could hydrolyse relatively high concentrations of sucrose almost quantitatively for more than 60 days.

Polyclonal‐antibody‐mediated insolubilization and stabilization of papain

Antisera raised in rabbits against native iodoacetamide‐ and iodoacetic acid‐modified papain contained precipitating and non‐inhibitory antibodies. Papain could be insolubilized as enzyme–antibody adducts with the γ‐globulin fraction derived from the antiserum. Two insolubilized papain preparations, designated A and B, with low and high antibody/enzyme ratios, respectively, exhibited high enzyme activity and markedly enhanced thermal and denaturant stabilities. However, papain antibody adduct B was superior in activity and stability over preparation A. The usefulness of immobilized papain in biopharmaceutical and other industries is also discussed.

Molecular mechanisms of drug photodegradation and photosensitization.

Drug-induced photosensitivity of the skin is drawing increasing attention. In past few decades, photosensitivity has been reported with an array of drugs, and is now recognized as a noteworthy medical problem by clinicians, regulatory authorities and pharmaceutical industry. The photosensitivity is of two types i.e., phototoxicity and photoallergy. Phototoxic disorders have a high incidence, whereas photoallergic reactions are much less frequent in human population. Several hundred substances, chemicals, or drugs may invoke phototoxic and photoallergic reactions. In order to avoid photosensitive reactions, it is essential to understand the mechanism behind the photosensitizing properties of such substances before these drugs are introduced in clinical settings. Photosensitization is inter-related to photochemical reaction, through the knowledge of which the photosensitivity of a drug can be anticipated. This review highlights the current research status on photosensitizing drugs and its correlation to phototoxicity. Different mechanisms of photodegradation of photolabile drugs have also been discussed.

Immobilization of the restriction endonuclease EcoRI usefulness of a polyclonal antibody support

Abstract The restriction enzyme Eco RI has been immobilized by using an immunoaffinity-based procedure on Sepharose 4B. The antibody support, prepared by coupling the γ-globulin fraction of serum of immunized rabbits to CNBr-activated Sepharose-4B, was highly effective in binding Eco RI from solution although only about half of the bound activity appeared to be expressed by the immobilized preparations. Restriction activity of Eco RI immobilized on the antibody support was indistinguishable from that of soluble enzyme on the linear λ-DNA and supercoiled plasmids pBR322 and pBHLUC P. Binding to the antibody support markedly enhanced the resistance of Eco RI to heat inactivation, and the preparation, unlike the native enzyme, retained significant activity after exposure to a temperature of 65°C. It was also possible to immobilize Eco RI directly from the cell lysates of Escherichia coli pMB4, an Eco RI overproducing strain. The immobilized preparation did not possess nonspecific nuclease activity that was prominent in the lysates, suggesting specificity in the binding of Eco RI to the antibody support.

Reaction of phenyl(trihalomethyl)mercury compounds with n-unsubstituted sulfoximines

Abstract Reaction of phenyl(tribromomethyl)mercury and phenyl(bromodichloromethyl)mercury with sulfoximines gives the corresponding oxosulfonium ylide as the major product along with the respective sulfoxide and tetrahaloethylene as minor products.

Synthesis ofGEM-dibromocyclopropanoid fatty esters using phenyl (tribromomethyl) mercury

Thegem-dibromocyclopropanation of naturally occurring unsaturated hydroxy fatty esters, methyl ricinoleate (I) and methyl isoricinoleate (II), has been undertaken to provide compounds which might have potential utility. Phenyl(tribromomethyl)mercury reacts only with the carbon-carbon double bond of each substrate, leaving the OH group intact. The product, methyl 9,10-dibromomethylene-12-hydroxyoctadecanoate (III) and methyl 12,13-dibromomethylene-9-hydroxyoctadecanoate (IV), obtained from I and II, respectively, were characterized by elemental, infrared (IR) and nuclear magnetic resonance (NMR) analyses.

Studies on the inactivation of soluble and immobilized papain by the ascorbic acid–Cu2+ system: a model to propose the effect of free radicals on membrane-bound enzymes in vivo

Free radicals have been suggested to be widely implicated as the species responsible for harmful biological processes, such as aging, carcinogenesis and numerous other diseases. The mechanism of biological damage produced in such processes has been investigated in a wide variety of systems, including studies on proteins, enzymes, nucleic acids and carbohydrates. In the present study we selected an ascorbic acid–transition‐metal ion (ASA–Cu2+) system in order to understand the mechanism of soluble and membrane‐bound enzyme inactivation by generating free radicals. Papain, a thiol protease, was immobilized on an immobilized‐metal‐ion carrier and used as a model to examine the inactivation behaviour of membrane‐bound enzymes. A comparison was made between the inactivation of soluble and immobilized papain by free radicals, and the potential of different radical scavengers to prevent the inactivation of enzyme was examined.

Photoinduced electron transfer photodegradation of photosensitive diuretic drug-xipamide

Abstract Xipamide (1), a photosensitive diuretic drug is photolabile under anaerobic conditions and with UVA light. In the present study the photochemical behavior of xipamide was investigated in the presence of both electron donor and acceptor. When xipamide (1) was irradiated with a high-pressure mercury lamp under anaerobic conditions in the presence of electron-donor N,N-dimethyl aniline (DMA) it afforded photoproduct 2 and in the presence of an electron-acceptor 1,4-dicyanonaphthalene (DCN) it afforded photoproduct 3. The product formation was explained through the photoinduced electron transfer mechanism. Products were isolated and identified on the basis of IR, NMR and mass spectral studies.