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At least 73 records · Page 4Linked to original sources
PubMed1994

Homology of 1-aminocyclopropane-1-carboxylate synthase, 8-amino-7-oxononanoate synthase, 2-amino-6-caprolactam racemase, 2,2-dialkylglycine decarboxylase, glutamate-1-semialdehyde 2,1-aminomutase and isopenicillin-N-epimerase with aminotransferases.

Profile analysis showed the title enzymes to be homologous with the aminotransferases. 1-Aminocyclopropane-1-carboxylate synthase is closely related to subgroup I of aminotransferases which includes aspartate, alanine, histidinol-phosphate, tyrosine and phenylalanine aminotransferase. 2,2-Dialkylglycine decarboxylase, glutamate-1-semialdehyde 2,1-aminomutase and 2-amino-6-caprolactam racemase are most similar to subgroup II which comprises aminotransferases with omega-amino acids as substrates. 8-Amino-7-oxononanoate synthase is closely related to both subgroup I and II, and isopenicillin-N-epimerase to subgroup IV with serine and phosphoserine aminotransferase. Aminotransferases and the title enzymes belong to a regio-specific family of evolutionarily related pyridoxal-5'-phosphate-dependent enzymes.

Acyltransferases↗
PubMed2002

Complexation between poly(maleic acid/octyl vinyl ether) and poly(vinyl caprolactam) in aqueous solution and at the alumina/water interface.

Solution and interfacial properties of binary polymer mixtures of poly(maleic acid/octyl vinyl ether) (PMAOVE) and poly(vinyl caprolactam) (PVCAP) have been studied for the alumina/water system. To test the hydrophobic effect, mixtures of poly(maleic acid/methyl vinyl ether) (PMAMVE) and PVCAP are also investigated and compared to the behavior of PMAOVE/PVCAP. At low pH, both polymer mixtures become turbid upon mixing. The turbidity increases at low mixing ratios of PVCAP to the vinyl ether component, reaches a maximum, and then decreases at higher mixing ratios. Upon shifting the pH to the alkaline range, i.e., pH 7.5 and above, the turbid solution becomes clear for both the polymer mixtures. Cloud point measurements indicate the absence of complexation of PVCAP with PMAMVE under the alkaline conditions, but strong interaction with PMAOVE. This is attributed to the different forces involved in the complexation among the polymers: H bonding for PVCAP/PMAMVE and both H bonding and hydrophobic effects for PVCAP/PMAOVE. At the alumina/water interface, the normally nonadsorbing PVCAP is triggered to adsorb by PMAOVE, attributed to the hydrophobic complexation between the two. However, the adsorption of PVCAP shows a maximum as a function of the concentration of PMAOVE. At concentrations of PMAOVE above the onset of its own plateau adsorption, the amount of PVCAP triggered to adsorb is reduced possibly due to the polymer complex formation in solution.

Journal Article↗
PubMed2004

Hydrogen bond driven chemical reactions: Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water.

Recent experiments have shown that supercritical water (SCW) has the ability to accelerate and make selective synthetic organic reactions, thus replacing the common but environmentally harmful acid and basic catalysts. In an attempt to understand the intimate mechanism behind this observation, we analyze, via first-principles molecular dynamics, the Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water, for which accurate experimental evidence has been reported. Differences in the wetting of the hydrophilic parts of the solute, enhanced by SCW, and the disrupted hydrogen bond network are shown to be crucial in triggering the reaction and in making it selective. Furthermore, the enhanced concentrations of H(+) in SCW play an important role in starting the reaction.

Journal Article↗
PubMed2005

Dynamic kinetic resolution of amino acid amide catalyzed by D-aminopeptidase and alpha-amino-epsilon-caprolactam racemase.

Amino acid amide racemizing activity was discovered in alpha-amino-epsilon-caprolactam (ACL) racemase (EC 5. 1. 1. 15) from Achromobacter obae. The enzymatic synthesis of d-alanine from l-alanine amide has been demonstrated by use of d-aminopeptidase (DAP; EC 3. 4. 11. 19) from Ochrobactrum anthropi C1-38 and ACL racemase. The conversion of 45 mM l-alanine amide was carried out at 30 degrees C for 7 h; l-alanine amide was completely converted to d-alanine, and no l-alanine was detected. The result of successive enzymatic reaction shows that the combination of ACL racemase and DAP can be applied for dynamic kinetic resolution of dl-amino acid amides to yield d-amino acids.

Achromobacter↗
PubMed2006

The oxidative mannich reaction catalyzed by dirhodium caprolactamate.

Dirhodium caprolactamate [Rh2(cap)4] is a highly effective catalyst for the oxidative Mannich reaction. The reaction proceeds via C-H oxidation of a tertiary amine followed by nucleophilic capture. This green transformation is conducted in protic solvent using inexpensive T-HYDRO (70% t-BuOOH in water). Synthetically valuable gamma-aminoalkyl butenolides are obtained.

Catalysis↗
PubMed2005

Reversible flocculation of silica across the phase boundary of poly(vinyl caprolactam) in aqueous solution.

The colloid stability of silica dispersions in water in the presence of poly(vinyl caprolactam) (PVCAP) has been studied below and above the lower consolute temperature (LCT) of its solutions. The dispersion sediments slowly without PVCAP in the temperature range studied (26-40 degrees C) or with PVCAP below the LCT ( approximately 30 degrees C). In contrast, with PVCAP above the LCT, rapid flocculation occurs at acid pH, with re-dispersal on cooling. Reversible flocculation is also obtained above the LCT by cycling the pH from alkaline to acid and back. The flocculation observed above the LCT may also be regarded as heterocoagulation between the silica particles and the aggregates of the polymer.

Journal Article↗
PubMed2004

N-(phenylthio)-epsilon-caprolactam: a new promoter for the activation of thioglycosides.

N-(phenylthio)-epsilon-caprolactam (1) has been applied as a new promoter for the activation of thioglycosides. This proceeds by the reaction of 1 with trifluoromethansulfonic anhydride, which subsequently activates the thioglycoside for glycosidic bond formation. Notably, the reaction proceeds efficiently at room temperature and is adaptable to our reactivity-based one-pot oligosaccharide synthesis. [reaction: see text]

Carbohydrate Sequence↗
PubMed2005

Efficient aziridination of olefins catalyzed by mixed-valent dirhodium(II,III) caprolactamate.

[reaction: see text] A mild, efficient, and selective aziridination of olefins catalyzed by dirhodium(II) caprolactamate [Rh(2)(cap)(4).2CH(3)CN] is described. Use of p-toluenesulfonamide (TsNH(2)), N-bromosuccinimide (NBS), and potassium carbonate readily affords aziridines in isolated yields of up to 95% under extremely mild conditions with as little as 0.01 mol % Rh(2)(cap)(4). Aziridine formation occurs through Rh(2)(5+)-catalyzed aminobromination and subsequent base-induced ring closure. An X-ray crystal structure of a Rh(2)(5+) halide complex, formed from the reaction between Rh(2)(cap)(4) and N-chlorosuccinimide, has been obtained.

Alkenes↗
PubMed2005

Benzylic oxidation catalyzed by dirhodium(II,III) caprolactamate.

[reaction: see text] Dirhodium caprolactamate [Rh2(cap)4] is an effective catalyst for benzylic oxidation with tert-butyl hydroperoxide (TBHP) under mild conditions. Sodium bicarbonate is the optimal base additive for substrate conversion. Benzylic carbonyl compounds are readily obtained, and a formal synthesis of palmarumycin CP2 using this methodology is described.

Benzene Derivatives↗
PubMed2002

Separation and characterisation of caprolactam-formaldehyde reaction products.

Methylolation and condensation products formed in caprolactam-formaldehyde reaction mixtures have been identified using nuclear magnetic resonance (NMR) and mass spectrometry (MS). Previously unreported side-products were also detected. All of the reaction products were separated by micellar electrokinetic chromatography (MEKC) and high performance liquid chromatography (HPLC), and the separation parameters, such as efficiency and distribution constants, obtained in the two techniques were compared. For quantification, the response factors for the monomers were determined using standard calibration and hydrolysis, whilst those for the condensation products were deduced from the values of the monomers. The accurate determination of the response factors was confirmed by checking the mass balance of a known mixture.

Journal Article↗
PubMed1989

Caprolactam and benzoin: tests for induction of chromosome aberrations and SCEs in mouse bone marrow.

CAP and ZOIN were tested in vivo for their ability to induce sister-chromatid exchanges (SCE) and chromosome aberrations in mouse bone marrow cells. Single intraperitoneal injections of ZOIN to a maximum of 3000 mg/kg body weight failed to increase the number of SCEs in metaphases recovered 24 h post-treatment, and doses of 1500 mg/kg did not induce measurable increases in chromosome-aberration levels among first-division metaphases at 18 h. Similarly, neither endpoint showed a significant increase following near-lethal doses of 700 mg/kg of CAP. Two lower doses of each chemical were also ineffective. Under the in vivo conditions of our test system, both chemicals were cytogenetically inactive.

Animals↗
PubMed1989

Assessment of unscheduled DNA synthesis in Fischer 344 rat pachytene spermatocytes exposed to caprolactam or benzoin in vivo.

Male Fischer 344 rats were treated with the non-carcinogenic chemicals CAP and ZOIN. The spermatogenic cells were isolated at selected times post-exposure for assessment of chemically-induced DNA damage by quantitative autoradiography of unscheduled DNA synthesis (UDS). Neither chemical (750 mg/kg administered by gavage) induced UDS in pachytene spermatocytes isolated 12, 24 or 48 h after treatment.

Animals↗