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Hydroxy Acids (hydroxy + acid)
Selected AbstractsPolymerization of ,-Hydroxy Acids by RibosomesCHEMBIOCHEM, Issue 17 2008Atsushi Ohta Abstract Over 30 years ago, Fahnestock and Rich reported intriguing data showing the capability of the ribosome to polymerize phenyllactic acid. Although the polymerization was initiated and terminated randomly on polyuridic acids, the given data convincingly suggested that the generated polymer was composed of an approximately 7:3 mixture of phenyllactic acid and phenylalanine. Despite the fact that Fahnestock's conclusion was very likely correct, there have been no reports to follow up the ribosome-catalyzed polymerization of ,-hydroxy acids until very recently. At the end of 2007, we reported messenger RNA (mRNA)-directed polyester synthesis by using the new emerging method of genetic-code reprogramming in which , -hydroxy acids with various kinds of side-chains are assigned to arbitrarily chosen codons. In this work, we have achieved the ribosomal synthesis of polyesters with the sequence composition and length in a fully controlled manner according to the sequence of mRNA. This Concept article describes the background of the method development and its application to the synthesis of polyesters. [source] ChemInform Abstract: Synthesis of Tertiary ,-Hydroxy Acids by Silylene Transfer to ,-Keto Esters.CHEMINFORM, Issue 13 2008Brett E. Howard Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Titanium(IV) Alkoxide Ligand Exchange with ,-Hydroxy Acids: The Enantioselective Aldol Addition.CHEMINFORM, Issue 14 2001Rainer Mahrwald Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Macrolactonization of Hydroxy Acids Using a Polymer Bound Carbodiimide.CHEMINFORM, Issue 9 2001Gary E. Keck Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ,-Hydroxy acids, ,-hydroxy acid, and other topical agentsDERMATOLOGIC THERAPY, Issue 2 2000Zoe Diana Draelos First page of article [source] Topical revitalization of body skinJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 4 2000Timothy Corcoran Flynn Abstract Topical treatments for the body are beneficial for photoageing as well as for specific disease processes, such as scars or striae. Every patient should topically apply photoprotectants in order to prevent photodamage to the skin. Tretinoin can improve body skin and has a documented use in striae. ,-Hydroxy acids can restore body skin when used on a regular basis. Antioxidants may be of benefit. Scars can be improved with a variety of topically applied agents ranging from silicone gel sheeting to super-potent topical steroids. Chemical peeling for the body can improve the skin with the use of ,- or ,-hydroxy acids. While topical therapy can improve body skin, adjunctive surgical therapy may be needed to correct body skin disorders or concerns fully. [source] Preparation of Optically Active (Acyloxy)alkyl Esters from Optically Active O-Acyl-,-hydroxy Acids.CHEMINFORM, Issue 43 2002Peter R. Guzzo Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Stereoselective Cyanation of Chiral ,-Amino Aldehydes by Reaction with Nagata,s Reagent: A Route to Enantiopure ,-Amino-,-hydroxy Acids.CHEMINFORM, Issue 31 2001Jose M. Andres Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Lactic Acid Chemical Peels as a New Therapeutic Modality in Melasma in Comparison to Jessner's Solution Chemical PeelsDERMATOLOGIC SURGERY, Issue 12 2006KHALIFA E. SHARQUIE MBCHB BACKGROUND Many chemicals have been used in the skin peeling for melasma such as Jessner's solution and glycolic acid. Lactic acid is an ,-hydroxy acid that has not been used before in chemical peeling of melasma. OBJECTIVE The purpose of the present work was to evaluate the efficacy and safety of lactic acid in chemical peeling of melasma in comparison to Jessner's solution chemical peels. METHODS This study was conducted at the Department of Dermatology and Venereology, Baghdad Hospital, in the period between April 2001 and August 2002. Thirty patients with melasma were included in this study. They were mostly of skin type IV according to Fitzpatrick's classification, 26 (86.67%) were women, and 4 (13.33%) were men, with an age range from 18 and 50 years (mean±SD, 33.53±6.96 years). Full clinical examination was done to all patients including Wood's light. The severity of melasma was assessed by MASI (Melasma Area Severity Index). Pure lactic acid full strength (92%, pH 3.5) was used as a new peeling agent on the left side of the face while Jessner's solution was applied to the right side of the face. The chemical peeling sessions were done every 3 weeks until the desired response was achieved. Follow-up was carried out for 6 months after the last session. RESULTS Six patients were defaulted from the study after the first session for unknown reasons. Twenty-four patients completed the study. Twenty (83.33%) were women and four were men (16.67%). Wood's light examination showed increased contrast in all patients of mostly epidermal melasma. The number of sessions ranged from 2 to 5. All patients showed marked improvement as calculated by MASI score before and after treatment, and the response was highly statistically significant. No side effect was recorded in all treated patients. CONCLUSION Lactic acid was found to be an effective and safe peeling agent in the treatment of melasma, and it was as effective as Jessner's solution. [source] ,-Hydroxy acids, ,-hydroxy acid, and other topical agentsDERMATOLOGIC THERAPY, Issue 2 2000Zoe Diana Draelos First page of article [source] A Post-Modification Strategy for the Synthesis of Uniform, Hydrophilic/Hydrophobic Patterned ,-Hydroxy Acid OligomersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2009Nadja Franz Abstract Hydrophilic/hydrophobic patterning is a well-established design strategy to guide secondary structure formation of both natural as well as non-natural oligomers and polymers. This contribution explores the feasibility of a new approach for the synthesis of uniform, sequence-defined, hydrophilic/hydrophobic patterned oligo(,-hydroxy acid)s. The proposed strategy is based on post-modification of a reactive oligoester scaffold composed of an alternating sequence of hydrophobic [(2S)-2-hydroxy-4-methylpentanoic acid] and masked hydrophilic [(2S)-2-hydroxypent-4-enoic acid] ,-hydroxy acids. The use of (2S)-2-hydroxypent-4-enoic acid instead of a complex side-chain-protected hydrophilic building block obviates the need for additional protective group chemistry during chain extension. In a subsequent post-modification step, the allyl side chains can be quantitatively modified via free-radical addition of different ,-functional thiols to afford hydrophilic/hydrophobic patterned oligoesters. The proposed synthetic strategy provides an interesting alternative to rapidly generate libraries of foldamers with identical chain length and monomer sequence but different side-chain functionalities.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Studies on the oxygen atom transfer reactions of peroxomonosulfate: Catalytic effect of hemiacetalINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2009S. Shailaja The reaction of peroxomonosulfate (PMS) with glycolic acid (GLYCA), an alpha hydroxy acid, in the presence of Ni(II) ions and formaldehyde was studied in the pH range 4.05,5.89 and at 31°C and 38°C. When formaldehyde and Ni(II) ions concentrations are ,5.0 × 10,4 M to 10.0 × 10,4 M, the reaction is second order in PMS concentration. The rate is catalyzed by formaldehyde, and the observed rate equation is (,d[PMS])/dt = (k,2[HCHO][Ni(II)][PMS]2)/{[H+](1+K2[GLYCA])}. The number of PMS decomposed for each mole of formaldehyde (turnover number) is 5,10, and the major reaction product is oxygen gas. The first step of the reaction mechanism is the formation of hemiacetal by the interaction of HCHO with the hydroxyl group of nickel glycolate. The peroxomonosulfate intermediate of the Ni-hemiacetal reacts with another molecule of PMS in the rate-limiting step to give the product. This reaction is similar to the thermal decomposition of PMS catalyzed by Ni(II) ions. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 642,649, 2009 [source] Studies on the oxygen atom transfer reactions of peroxomonosulfate: Oxidation of glycolic acidINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2009S. Shailaja The kinetics of oxidation of glycolic acid, an ,-hydroxy acid, by peroxomonosulfate (PMS) was studied in the presence of Ni(II) and Cu(II) ions and in acidic pH range 4.05,5.89. The metal glycolate, not the glycolic acid (GLYCA), is oxidized by PMS. The rate is first order in [PMS] and metal ion concentrations. The oxidation of nickel glycolate is zero-order in [GLYCA] and inverse first order in [H+]. The increase of [GLYCA] decreases the rate in copper glycolate, and the rate constants initially increase and then remain constant with pH. The results suggest that the metal glycolate ML+ reacts with PMS through a metal-peroxide intermediate, which transforms slowly into a hydroperoxide intermediate by the oxygen atom transfer to hydroxyl group of the chelated GLYCA. The effect of hydrogen ion concentrations on kobs suggests that the structure of the metal-peroxide intermediates may be different in Ni(II) and Cu(II) glycolates. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 160,167, 2009 [source] Expression of 3-hydroxyisobutyrate dehydrogenase in cultured neural cellsJOURNAL OF NEUROCHEMISTRY, Issue 4 2008Radovan Murín Abstract The branched-chain amino acids (BCAAs) , isoleucine, leucine, and valine , belong to the limited group of substances transported through the blood,brain barrier. One of the functions they are thought to have in brain is to serve as substrates for meeting parenchymal energy demands. Previous studies have shown the ubiquitous expression of a branched-chain alpha-keto acid dehydrogenase among neural cells. This enzyme catalyzes the initial and rate-limiting step in the irreversible degradative pathway for the carbon skeleton of valine and the other two branched-chain amino acids. Unlike the acyl-CoA derivates in the irreversible part of valine catabolism, 3-hydroxyisobutyrate could be expected to be released from cells by transport across the mitochondrial and plasma membranes. This could indeed be demonstrated for cultured astroglial cells. Therefore, to assess the ability of neural cells to make use of this valine-derived carbon skeleton as a metabolic substrate for the generation of energy, we investigated the expression in cultured neural cells of the enzyme processing this hydroxy acid, 3-hydroxyisobutyrate dehydrogenase (HIBDH). To achieve this, HIBDH was purified from bovine liver to serve as antigen for the production of an antiserum. Affinity-purified antibodies against HIBDH specifically recognized the enzyme in liver and brain homogenates. Immunocytochemistry demonstrated the ubiquitous expression of HIBDH among cultured glial (astroglial, oligodendroglial, microglial, and ependymal cells) and neuronal cells. Using an RT-PCR technique, these findings were corroborated by the detection of HIBDH mRNA in these cells. Furthermore, immunofluorescence double-labeling of astroglial cells with antisera against HIBDH and the mitochondrial marker pyruvate dehydrogenase localized HIBDH to mitochondria. The expression of HIBDH in neural cells demonstrates their potential to utilize valine imported into the brain for the generation of energy. [source] Enlarging the library of poly-(L -lysine citramide) polyelectrolytic drug carriersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2001Anne-Claude Couffin-Hoarau Abstract Poly-(L -lysine citramide) is a degradable drug carrier of the polyelectrolyte type that is composed of citric acid and L -lysine building blocks. In a previous work, poly-(L -lysine citramide) was synthesized by the interfacial polycondensation of ,-hydroxy acid protected citryl dichloride with COOH-protected lysine diamine. Because of head-to-head and head-to-tail and tail-to-tail linkages in the chains as well as various side reactions such as deprotection of the ,-hydroxy acid moieties and intramolecular imide ring formation, a very large family of degradable polyelectrolyte copolymers was obtained. All the members of this family hydrolytically degrade to the same end products. In this study, another route was explored based on the polycondensation of ,-hydroxy acid protected citric acid pentafluorophenyl diesters, namely, citrobenzal dipentafluorophenyl and citrochloral dipentafluorophenyl with N - N,-trimethylsilylated COOH-protected L -lysine. The resulting polymers were characterized by IR, NMR, and size exclusion chromatographic analyses. The resulting chain structures and repeat units were identified from these characterizations and are discussed as compared with characteristics exhibited by analogous polymers resulting from interfacial polycondensation. Differences observed at the intermediate stage involving protected polymers were largely erased during the final deprotection stage because of imide formation during final hydrolysis under the selected conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3475,3484, 2001 [source] Pharmacokinetic Investigation of a 14C-Labelled ,3/, Tetrapeptide in RatsCHEMISTRY & BIODIVERSITY, Issue 11 2004Hansjörg Wiegand The solid-phase synthesis and an ADME investigation with albino and pigmented male rats of the doubly 14C-labelled ,/, -tetrapeptide derivative Ac- ,3hTyr-(D)Trp- ,3hLys- ,3hThr-lactone (3; Fig.,3) are described. After intravenous (i.v.) and peroral (p.o.) administration of the peptide, its concentration in blood and plasma, its tissue distribution, and the metabolism and the excretion of the peptide were analyzed over a period of up to 7,days post dose. The tetrapeptide in its ring opened form, 5, has a bioavailability of ca. 25%; radioactivity is distributed in the animals in an organ-specific way, and the compound appears to pass the blood-brain barrier to a very small extent, if at all (Tables,1,3 and Figs.,2,6). Excretion (37% renal, 44% fecal, including biliary) of the tetrapeptide 4,days after i.v. administration is almost complete, with only 4.3% remaining in the carcass; 4,days after p.o. administration 97% of the dose has been excreted in the feces. Radiochromatograms taken of plasma (0.5 and 24,h after i.v. dosing) and of urine and feces extracts (0,48,h collected) reveal the presence of lactone 3 and/or the corresponding hydroxy acid 5 with essentially no or very minor other peaks, respectively, representing possible metabolites (Tables,4,6, and Fig.,7 and 8). A comparison with a previous ADME investigation of a , -nonapeptide show that , except for the lack of metabolism , all aspects of exposure, distribution, and elimination are different (structure-specific properties). The investigated tetrapeptide 3 is a potent and highly specific agonist of the somatostatin receptor hsst4, rendering the results described herein promising for diagnostic and therapeutic applications of , -peptides. [source] Glycolic Acid Treatment Increases Type I Collagen mRNA and Hyaluronic Acid Content of Human SkinDERMATOLOGIC SURGERY, Issue 5 2001Eric F. Bernstein MD Background. Chronic solar irradiation results in both morphologic and functional changes in affected skin. ,-hydroxy acids, such as glycolic acid, have been shown to improve photodamaged skin. Objective. To investigate alterations in collagen gene induction and epidermal and dermal hyaluronic acid production as a result of administered glycolic acid. Methods. In this study we compared collagen gene expression from skin biopsy specimens, and epidermal and dermal hyaluronic acid immunohistochemical staining between glycolic acid-treated and vehicle-treated skin. Forearm skin was treated with 20% glycolic acid lotion or a lotion vehicle control twice a day for 3 months. Results. Epidermal and dermal hyaluronic acid and collagen gene expression were all increased in glycolic acid-treated skin as compared to vehicle-treated controls. Conclusion. Our data suggest that epidermal and dermal remodeling of the extracellular matrix results from glycolic acid treatment. Longer treatment intervals may result in collagen deposition as suggested by the measured increase in mRNA. [source] Enantioseparation of amino acids, ,-hydroxy acids, and dipeptides by ligand-exchange CEC using silica-based chiral stationary phasesELECTROPHORESIS, Issue 16 2009Elfriede Pittler Abstract This work deals with the application of silica-based ligand-exchange chiral stationary phases (CSPs) for the enantioseparation of underivatised amino acids, ,-hydroxy acids, and dipeptides with packed CEC. Two different possibilities of preparing silica-based CSPs are presented. One phase contains L -4-hydroxyproline chemically bonded via a spacer to 3,,m silica material. The other approach makes use of N -decyl- L -4-hydroxyproline dynamically coated on a reversed-phase packed capillary. Dynamical coating of reversed-phase material represents a simple alternative to prepare CSP. A comparison of the chemically bonded phase with the dynamically coated CSP by means of resolution of complex-forming analytes is presented. The chemically bonded phase was found to be superior to the dynamically coated phase in terms of resolution of amino acids and dipeptides. However, the dynamically coated CSP was found to be especially suitable for the separation of ,-hydroxy acids. Both techniques are applicable for enantiomer purity tests. [source] Role of the charge in continuous beds in the chiral separation of hydroxy acids by ligand-exchange capillary electrochromatographyELECTROPHORESIS, Issue 17 2003Oliver Lecnik Abstract This paper deals with the chiral separation of hydroxy acids using diallyl-dimethylammonium chloride as a positive charge-providing agent in the continuous bed. The chiral continuous bed was prepared by in situ copolymerization of monomers, including an L -4-hydroxyproline derivative as a chiral selector. This phase was applied to the chiral separation of hydroxy monocarboxylic acids and hydroxy dicarboxylic acids, respectively. The influence of both the selector concentration and the charge-providing agent on retention and separation was investigated. [source] A Post-Modification Strategy for the Synthesis of Uniform, Hydrophilic/Hydrophobic Patterned ,-Hydroxy Acid OligomersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2009Nadja Franz Abstract Hydrophilic/hydrophobic patterning is a well-established design strategy to guide secondary structure formation of both natural as well as non-natural oligomers and polymers. This contribution explores the feasibility of a new approach for the synthesis of uniform, sequence-defined, hydrophilic/hydrophobic patterned oligo(,-hydroxy acid)s. The proposed strategy is based on post-modification of a reactive oligoester scaffold composed of an alternating sequence of hydrophobic [(2S)-2-hydroxy-4-methylpentanoic acid] and masked hydrophilic [(2S)-2-hydroxypent-4-enoic acid] ,-hydroxy acids. The use of (2S)-2-hydroxypent-4-enoic acid instead of a complex side-chain-protected hydrophilic building block obviates the need for additional protective group chemistry during chain extension. In a subsequent post-modification step, the allyl side chains can be quantitatively modified via free-radical addition of different ,-functional thiols to afford hydrophilic/hydrophobic patterned oligoesters. The proposed synthetic strategy provides an interesting alternative to rapidly generate libraries of foldamers with identical chain length and monomer sequence but different side-chain functionalities.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Multi-Step Synthesis and Biological Evaluation of Analogues of Insulin Secretagogue (2S,3R,4S)-4-HydroxyisoleucineEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2009Kaïss Aouadi Abstract A series of stereochemically defined analogues of (2S,3R,4S)-4-hydroxyisoleucine and related ,-hydroxy acids have been prepared by multi-step routes from D -glucose, whereas ketolization between TBDMS-protected hydroxypropanone and ethyl isocyanoacetate led to racemic analogues. Bioassays showed that of eight newly synthesized compounds, two of them presented an interesting statistical trend to increase glucose-induced insulin secretion when tested in isolated rat pancreatic islets in the presence of 8.3 mM glucose and at a concentration of 200 ,M, which has previously been shown to be effective for (2S,3R,4S)-4-hydroxyisoleucine.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Stimulation of epidermal calcium gradient loss and increase in TNF-, and IL-1, expressions by glycolic acid in murine epidermisEXPERIMENTAL DERMATOLOGY, Issue 8 2005Se Kyoo Jeong Abstract:, In a previous study, we reported that ,-hydroxy acids (AHA), such as glycolic acid and lactic acid, did not induce any significant changes in transepidermal water loss for normal murine skin. The ultrastructural observations, however, showed that the extent of lamellar body exocytosis significantly increased. Because AHA can theoretically decrease the calcium ion concentration by chelation, topical AHA may induce the loss of epidermal calcium gradient by lowering the calcium ion concentration in the granulocytes and, subsequently, induce lamellar body secretion. The aim of this study is to verify that glycolic acid could modulate the epidermal calcium gradient and increase lamellar body exocytosis. Seventy per cent of glycolic acid aqueous solution was applied to the normal skin of hairless mice and biochemical and morphological studies were performed. The loss of epidermal calcium gradient was observed in glycolic-acid-applied skin of hairless mice and subsequent barrier function recovery processes, such as an increase in lamellar body secretion, were observed. The extracellular glycolic acid was found to inhibit the change in intracellular calcium ion concentration in response to extracellular calcium ion concentration changes in the cultured mouse keratinocyte in vitro. The protein and mRNA expressions of tumour necrosis factor-, and interleukin-1, in the murine epidermis were significantly increased after glycolic acid application. An in vitro study using cultured keratinocytes suggested that glycolic acid could lower the calcium ion concentration, at least in part, through the chelating effects of the glycolic acid on the cationic ions. [source] Kinetics and mechanism of the oxidation of some ,-hydroxy acids by 2,2,-bipyridinium chlorochromateINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2002Vinita Kumbhat The oxidation of glycolic, lactic, malic, and a few substituted mandelic acids by 2,2,-bipyridinium chlorochromate (BPCC) in dimethylsulphoxide leads to the formation of corresponding oxoacids. The reaction is first order each in BPCC and the hydroxy acids. The reaction is catalyzed by the hydrogen ions. The hydrogen ion dependence has the form: kobs = a + b [H+]. The oxidation of ,-deuteriomandelic acid exhibited a substantial primary kinetic isotope effect (kH/kd = 5.29 at 303 K). Oxidation of p -methylmandelic acid was studied in 19 different organic solvents. The solvent effect has been analyzed by using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 248,254, 2002 [source] Evaporation of a model skin lotion with beta-hydroxy acidsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2004A. Al Bawab Synopsis Two , -hydroxy acids, malic and salicylic acids were combined with a non-ionic surfactant, a commercial pentaoxyethylene sorbitan mono-oleate and water to form a simple model of a skin lotion and the phase diagrams were determined. One emulsion formulation with relative amounts of the three components similar to those in commercial lotions was used to observe microscopically the changes in the emulsion structure during evaporation. The microscope images were subsequently compared to the information from the phase diagram under equilibrium conditions. The results showed the behavior of the systems of the two acids to be distinctly different; as exemplified by that of a typical formulation with 3% by weight of acid and 5% of surfactant. The malic acid system consisted of vesicles, exclusively formed by the surfactant and water, in an aqueous molecular solution of the acid and the initial evaporation resulted in an increase of the acid concentration in the aqueous solution to reach 35.5%, before solid crystals of the acid solid solution appeared. The salicylic acid formulation, on the other hand, already at the beginning of the determination consisted of water, particles of the acid solid solution and surfactant vesicles. In both cases the remaining deposit after total evaporation was particles of a solid acid solution and liquid surfactant. Résumé Deux acides , -hydroxy malique et salicylique ont été combinés avec un surfactant non ionique, un pentaoxyethylene sorbitan mono-oleate commercial et de l'eau pour former un model simple de lotion pour la peau. Leurs diagrammes de phase ont été déterminés. Une formule d'émulsion avec une quantité relative des trois composantes similaire a celles des lotions commerciales a été utilisée pour observer les changements microscopiques dans la structure de l'émulsion au cours de l,évaporation. Les images du microscope ont été ensuite comparées aux informations des diagrammes de phase dans les conditions d'équilibre. Les résultats ont montré que le comportement des systémes des deux acides est clairement différent, comme le montre l'exemple d'une formulation typique à 3% du poids d'acide et 5% du surfactant. Le système d'acide malique est constitué de vésicules exclusivement formées du surfactant et d'eau, dans une solution aqueuse moléculaire de l'acide, et l'évaporation initiale a eu comme consèquence l'augmentation de la concentration de l'acide en solution aqueuse qui a atteint 35.5% avant l'apparition des cristaux de la solution de l'acide solide. D'autre part la formulation de l'acide salicylique des le début de la détermination fut constituée d'eau, de particules de solution de l'acide solide et des vésicules du surfactant. Dans les deux cas les restes déposés après l'évaporation totale ètaient constitués des particules de la solution solide d'acide et du liquide surfactant. [source] Exploring the Biocatalytic Scope of Alditol Oxidase from Streptomyces coelicolorADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009W. van Hellemond Abstract The substrate scope of the flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2), recombinantly produced in Escherichia coli, was explored. While it has been established that AldO efficiently oxidizes alditols to D -aldoses, this study revealed that the enzyme is also active with a broad range of aliphatic and aromatic alcohols. Alcohols containing hydroxy groups at the C-1 and C-2 positions like 1,2,4-butanetriol (Km=170,mM, kcat=4.4,s,1), 1,2-pentanediol (Km=52,mM, kcat=0.85,s,1) and 1,2-hexanediol (Km=97,mM, kcat=2.0,s,1) were readily accepted by AldO. Furthermore, the enzyme was highly enantioselective for the oxidation of 1,2-diols [e.g., for 1-phenyl-1,2-ethanediol the (R)-enantiomer was preferred with an E -value of 74]. For several diols the oxidation products were determined by GC-MS and NMR. Interestingly, for all tested 1,2-diols the products were found to be the ,-hydroxy acids instead of the expected ,-hydroxy aldehydes. Incubation of (R)-1-phenyl-1,2-ethanediol with 18O-labelled water (H218O) revealed that a second enzymatic oxidation step occurs via the hydrate product intermediate. The relaxed substrate specificity, excellent enantioselectivity, and independence of coenzymes make AldO an attractive enzyme for the preparation of optically pure 1,2-diols and ,-hydroxy acids. [source] Insights into the mechanisms of flavoprotein oxidases from kinetic isotope effects,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 11-12 2007Paul F. Fitzpatrick Abstract Deuterium, solvent, and 15N kinetic isotope effects have been used to probe the mechanisms by which flavoproteins oxidize carbon,oxygen and carbon,nitrogen bonds in amines, hydroxy acids, and alcohols. For the amine oxidases D -amino acid oxidase, N -methyltryptophan oxidase, and tryptophan monooxygenase, D -serine, sarcosine, and alanine are slow substrates for which CH bond cleavage is fully rate limiting. Inverse isotope effects for each of 0.992,0.996 are consistent with a common mechanism involving hydride transfer from the uncharged amine. Computational analyses of possible mechanisms support this conclusion. Deuterium and solvent isotope effects with wild-type and mutant variants of the lactate dehydrogenase flavocytochrome b2 show that OH and CH bond cleavage are not concerted, but become so in the Y254F enzyme. This is consistent with a highly asynchronous reaction in which OH bond cleavage precedes hydride transfer. The results of Hammett analyses and solvent and deuterium isotope effects support a similar mechanism for alcohol oxidase. Copyright © 2007 John Wiley & Sons, Ltd. [source] Topical revitalization of body skinJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 4 2000Timothy Corcoran Flynn Abstract Topical treatments for the body are beneficial for photoageing as well as for specific disease processes, such as scars or striae. Every patient should topically apply photoprotectants in order to prevent photodamage to the skin. Tretinoin can improve body skin and has a documented use in striae. ,-Hydroxy acids can restore body skin when used on a regular basis. Antioxidants may be of benefit. Scars can be improved with a variety of topically applied agents ranging from silicone gel sheeting to super-potent topical steroids. Chemical peeling for the body can improve the skin with the use of ,- or ,-hydroxy acids. While topical therapy can improve body skin, adjunctive surgical therapy may be needed to correct body skin disorders or concerns fully. [source] Double-blind clinical study reveals synergistic action between alpha-hydroxy acid and betamethasone lotions towards topical treatment of scalp psoriasisJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 1 2000K Kostarelos Abstract Objective A double-blind, single-site, split-face clinical study was organized and carried out in order to evaluate the efficacy, tolerability, and safety of a glycolic acid containing scalp lotion in conjunction with a betamethasone (as the 17-valerate) scalp application against conditions of psoriasis. Background,-hydroxy acids (AHA) have been proposed as therapeutic modalities against skin exfoliative conditions such as ichthyosis, xeroderma, and psoriasis. AHAs are hereby clinically investigated as therapeutic modalities adjuvant to corticosteroids in order to diminish systemic and topical adverse side-effects most frequently associated with use of the latter. Methods Twenty patients suffering from scalp psoriasis and other psoriatic conditions were included in a double-blind, split-face clinical study, using combinations of a 10% (w/w) glycolic acid scalp lotion, placebo lotion (excipients only), and a 0.1% (w/w) betamethasone scalp application, applied twice daily without any bandage for a period of 8 weeks. Clinical assessments were carried out by highly experienced physician evaluations based on a four-grade scale, prior to treatment and after 2, 4, 6 and 8 weeks. Results Improvement was observed in all cases included in the study following treatment with the 10% glycolic acid lotion. However, when equal parts of the 0.1% betamethasone lotion were combined, most of the treated sites were healed. Moreover, the duration of treatment required for healing was in this case reduced to approximately half of that needed when the glycolic acid or the betamethasone lotions were used separately for treatment. Conclusions The present clinical study demonstrates for the first time that the effective and well tolerated therapeutic efficacy of glycolic acid scalp lotions is enhanced when used in conjunction with a 0.1% betamethasone scalp application against scalp psoriasis. This potential offers the practising dermatologist with novel treatment modes against severe skin conditions by combining topical corticosteroid with exfoliative agent therapy. [source] Polymerization of ,-Hydroxy Acids by RibosomesCHEMBIOCHEM, Issue 17 2008Atsushi Ohta Abstract Over 30 years ago, Fahnestock and Rich reported intriguing data showing the capability of the ribosome to polymerize phenyllactic acid. Although the polymerization was initiated and terminated randomly on polyuridic acids, the given data convincingly suggested that the generated polymer was composed of an approximately 7:3 mixture of phenyllactic acid and phenylalanine. Despite the fact that Fahnestock's conclusion was very likely correct, there have been no reports to follow up the ribosome-catalyzed polymerization of ,-hydroxy acids until very recently. At the end of 2007, we reported messenger RNA (mRNA)-directed polyester synthesis by using the new emerging method of genetic-code reprogramming in which , -hydroxy acids with various kinds of side-chains are assigned to arbitrarily chosen codons. In this work, we have achieved the ribosomal synthesis of polyesters with the sequence composition and length in a fully controlled manner according to the sequence of mRNA. This Concept article describes the background of the method development and its application to the synthesis of polyesters. [source] Chiral Encapsulation by Directional InteractionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Agnieszka Szumna Abstract The complexation of chiral guests in the cavity of dimeric self-assembled chiral capsule 12 was studied by using NMR spectroscopy and X-ray crystallography. Capsule 12 has walls composed of amino acid backbones forming numerous directional binding sites that are arranged in a chiral manner. The polar character of the interior dictates the encapsulation preferences towards hydrophilic guests and the ability of the capsule to extract guests from water into an organic phase. Chiral discrimination towards hydroxy acids was evaluated by using association constants and competition experiments, and moderate de values were observed (up to 59,%). Complexes with one or two guest molecules in the cavity were formed. For 1:1 complexes, solvent molecules are coencapsulated; this influences guest dynamics and makes the chiral recognition solvent dependent. Reversal of the preferences can be induced by coencapsulation of a nonchiral solvent in the chiral internal environment. For complexes with two guests, filling of the capsule's internal space can be very effective and packing coefficients of up to 70,% can be reached. The X-ray crystal structure of complex 12,((S) -6)2 with well-resolved guest molecules reveals a recognition motif that is based on an extensive system of hydrogen bonds. The optimal arrangement of interactions with the alternating positively and negatively charged groups of the capsule's walls is fulfilled by the guest carboxylic groups acting simultaneously as hydrogen-bond donors and acceptors. An additional guest molecule interacting externally with the capsule reveals a possible entrance mechanism involving a polar gate. In solution, the structural features and dynamic behavior of the D4 -symmetric homochiral capsule were analyzed by variable-temperature NMR spectroscopy and the results were compared with those for the S8 -symmetric heterochiral capsule. [source] | ||||||||||||||||