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Apical membrane Cl-butyrate exchange: Mechanism of short chain fatty acid stimulation of active chloride absorption in rat distal colon (1994)

Rajendran, V. M. ; Binder, H. J.

Springer

The journal of membrane biology 141 (1994), S. 51-58

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ISSN: 1432-1424

Keywords: Electroneutral ; Asymmetric anion exchange ; Butyrate-gradient-stimulated Cl uptake ; Cl-SCFA exchange

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract The cellular model of short chain fatty acid stimulation of electroneutral Na-Cl absorption in large intestine proposes that SCFA, following its uptake across the apical membrane, recycles and is coupled to functional Na-H and Cl-short chain fatty acid exchanges. To establish the presence of a Cl-butyrate exchange (used as a model short chain fatty acid), studies of 36Cl and 14C-butyrate uptake across apical membrane vesicles of rat distal colon were performed. An outward butyrate-gradient stimulated transient accumulation of 36Cl uptake that was not inhibited by pH clamping with valinomycin (a K ionophore) and FCCP (a proton ionophore). Outward butyrate-gradient-stimulated 36Cl uptake was inhibited by 4,4′-diisothiocyanatostilbene2,2′-disulfonic acid (DIDS) with a half-maximal inhibitory concentration (IC50) of 68.4 μm, and was saturated by both increasing extravesicular Cl concentration (K m for Cl of 26.8 ±3.4 mm and a V max of 12.4±0.6 nmol/mg protein·9 sec) and increasing intravesicular butyrate concentration (K m for butyrate of 5.9 mm and a V max for Cl of 5.9 nmol/mg protein · 9 sec). 36Cl uptake was also stimulated by outward gradients of other short chain fatty acids (e.g., propionate, acetate and formate). In contrast, an outward Cl gradient failed to enhance 14C-butyrate uptake. Extravesicular Cl more than extravesicular butyrate enhanced 36Cl efflux from apical membrane vesicles. These studies provide compelling evidence for the presence of an electroneutral, pH-activated, Cl-butyrate exchange which in concert with Na-H exchange is the mechanism by which butyrate stimulates electroneutral Na-Cl absorption.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00232873

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The alkaline degradation of cellobiose to glucose and fructose (1985)

Bonn, G. ; Binder, H. ; Leonhard, H. ; [et al.]

Springer

Monatshefte für Chemie 116 (1985), S. 961-971

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ISSN: 1434-4475

Keywords: Alkaline degradation ; Carbohydrates ; Kinetic studies

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Zusammenfassung Der alkalische Abbau von Cellobiose wurde mit 0.01N bis 0.1N NaOH im Temperaturbereich von 60 bis 85°C untersucht. Gleichzeitig wurden die gebildete Glucose und Fructose analysiert. Bei niedrigen Alkalikonzentrationen wird derpH Wert stark herabgesetzt, sodaß es innerhalb kurzer Reaktionszeiten zu einer Beendigung der Reaktion kommt. Bei höheren Alkalikonzentrationen ist diepH-Abnahme wesentlich geringer und der alkalische Abbau von Cellobiose gehorcht einer Reaktion 1. Ordnung. Durch die Anwendung eines vereinfachten Reaktionsschemas konnten auch die Folgereaktionen der Glucose- und Fructosebildung mathematisch erfaßt werden.

Notes: Abstract The alkaline degradation of cellobiose by 0.01 to 0.1N NaOH at temperatures between 60 and 85°C was studied. At the same time the formation of glucose and fructose was analyzed. At lower alkali concentrations, the production of acidic compounds lowered thepH to such an extent that the hydrolyzing reaction ceased within a relatively short time. At higher alkali concentrations thepH change is much smaller and first order reaction rates of the cellobiose degradation were obtained. Through the application of a simplified reaction mechanism the consecutive reactions of the glucose and fructose formation were evaluated mathematically.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00809189

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1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolan und 1,2-Bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborin: Synthese und Struktur sowie Berechnungen zur MolekülstrukturProfessor Hans-Georg von Schnering zum 65. Geburtstage gewidmet (1996)

Riegel, B. ; Hausen, H.-D. ; Schwarz, W. ; [et al.]

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 622 (1996), S. 1462-1470

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ISSN: 0044-2313

Keywords: 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane ; 1,2-bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine ; preparation ; NMR ; molecular structures ; ab initio calculations ; Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane and 1,2-Bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine: Synthesis and Structure as well as Calculations on the Molecular StructureThe diphosphides K2[(C6H5)P—(C6H5)P—P(C6H5)], 4 or K2[(tBuP)—(tBuP)2—P(tBu)], 5, react with (ClBNMe2)2 to form the binary 5-membered ring system 1,2-bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane (C6H5P)3(BNMe2)2, 2a, and the 6-membered ring system 1,2-bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine, (tBuP)4(BNMe2)2, 3a, respectively. 2a and 3a could be obtained in a pure form and characterized NMR spectroscopically and by X-ray structure analyses. The two ring systems are folded; 2a exists in the „envelope“- 3a in the „boat“-conformation. Ab initio computations for 3,4,5-triphospha-1,2-diborolane M5 show that the global minimum is characterized by one B—P double bond. The parent compound geometry M6 is characterized by transannular bonding in the PH—BH—BH—PH moiety which differs in character from those in the four- and five-membered rings (BH)2(PH)2 and (BH)2(PH)3 M5 d, respectively. Explicit calculation of the influence of amino substituents on boron improved agreement of the bond length between computed and X-ray data.

Notes: Die Diphosphide K2[(C6H5)P—(C6H5)P—P (C6H5)], 4, bzw. K2[(tBuP)—(tBuP)2—P(tBu)], 5, reagieren mit (ClBNMe2)2 zu dem binären Fünfringsystem 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolan (C6H5P)3(BNMe2)2, 2a, bzw. dem Sechsringsystem 1,2-Bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborin, (tBuP)4(BNMe2)2, 3a. 2a und 3a konnten in reiner Form isoliert, NMR-spektroskopisch und durch Röntgenstrukturanalysen charakterisiert werden. Beide Ringsysteme sind gefaltet; 2a zeigt eine „envelope“- 3a eine „Wannen“-Konformation.Ab initio Berechnungen an 3,4,5-Triphospha-1,2-diborolan M5 zeigen, daß im globalen Minimum eine B—P-Doppelbindung mit annähernd planarem σ3-Phosphor vorliegt. Die Geometrie der Stammverbindung des Sechsringes M6 weist „durch-den-Ring“-Bindung in der PH—BH—BH—PH-Baugruppe auf, welche sich von jenen im Vier- und Fünfring M5 d unterscheidet. Durch die explizite Berechnung des Einflusses von Aminosubstituenten an Bor auf die Geometrien des Fünf- und Sechsringes verbessert sich die Übereinstimmung der Bindungslängen mit den Daten der Röntgenstrukturanalyse.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/zaac.19966220906

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