151
|
Meshram HM, Kache R. Metalloclayzymes: An Efficient Oxidative Coupling of Thiols Catalysed by Fe (III) Montmorillonite in Buffer. SYNTHETIC COMMUN 1997. [DOI: 10.1080/00397919708004102] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
152
|
|
153
|
|
154
|
Kannan P, Pitchumani K, Rajagopal S, Srinivasan C. Sheet silicate catalysed demethylation and Fischer-Hepp rearrangement of N-methyl-N-nitrosoaniline. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1381-1169(96)00401-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
155
|
|
156
|
|
157
|
Silicates, Aluminates, and Phosphates. Inorg Chem 1997. [DOI: 10.1016/b978-012678550-0/50007-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
158
|
Krishna Maiti A, Bhattacharyya P. Montmorillonite Clay-catalysed Synthesis of Bis(indol-3-yl)-methanes and 1,2-Bis(indol-3-yl)ethanes†. JOURNAL OF CHEMICAL RESEARCH 1997. [DOI: 10.1039/a701355h] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
159
|
Mastalir Á, Notheisz F, Király Z, Bartók M, Dékány I. Novel clay intercalated metal catalysts: a study of the hydrogenation of styrene and 1-octene on clay intercalated Pd catalysts. STUDIES IN SURFACE SCIENCE AND CATALYSIS 1997. [DOI: 10.1016/s0167-2991(97)80940-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
|
160
|
Abstract
It has long been suspected that mineral surfaces may have been important in prebiotic chemistry. The recent demonstrations of extended oligomerization of nucleotides, amino acids and carbohydrates on mineral surfaces add support to the potential prebiotic importance of minerals, but leave a number of questions unanswered.
Collapse
Affiliation(s)
- A W Schwartz
- Evolutionary Biology Research Group, Faculty of Science, University of Nijmegen, Toernooiveld 1, 6525ED, Nijmegen, The Netherlands
| |
Collapse
|
161
|
Powell JJ, Ainley CC, Harvey RS, Mason IM, Kendall MD, Sankey EA, Dhillon AP, Thompson RP. Characterisation of inorganic microparticles in pigment cells of human gut associated lymphoid tissue. Gut 1996; 38:390-5. [PMID: 8675092 PMCID: PMC1383068 DOI: 10.1136/gut.38.3.390] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Macrophages at the base of human gut associated lymphoid tissue (GALT), become loaded early in life with dark granular pigment that is rich in aluminium, silicon, and titanium. The molecular characteristics, intracellular distribution, and source of this pigment is described. Laser scanning and electron microscopy showed that pigmented macrophages were often closely related to collagen fibres and plasma cells in GALT of both small and large intestine and contained numerous phagolysosomes, previously described as granules, that are rich in electron dense submicron sized particles. Morphological assessment, x ray microanalysis, and image electron energy loss spectroscopy showed three distinct types of microparticle: type I - spheres of titanium dioxide, 100-200 nm diameter, characterised as the synthetic food-additive polymorph anatase; type II - aluminosilicates, < 100-400 nm in length, generally of flaky appearance, often with adsorbed surface iron, and mostly characteristic of the natural clay mineral kaolinite; and type III - mixed environmental silicates without aluminium, 100-700 nm in length and of variable morphology. Thus, this cellular pigment that is partly derived from food additives and partly from the environment is composed of inert inorganic microparticles and loaded into phagolysosomes of macrophages within the GALT of all human subjects. These observations suggest that the pathogenicity of this pigment should be further investigated since, in susceptible individuals, the same intracellular distribution of these three types of submicron particle causes chronic latent granulomatous inflammation.
Collapse
Affiliation(s)
- J J Powell
- Gastrointestinal Laboratory, Rayne Institute, St Thomas' Hospital, London
| | | | | | | | | | | | | | | |
Collapse
|
162
|
Matsui M, Yamamoto H. Metal Ion-Exchanged Montmorillonites as Practical and Useful Solid Catalysts for the Synthesis ofα-Tocopherol. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1996. [DOI: 10.1246/bcsj.69.137] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
163
|
Pitsch S, Eschenmoser A, Gedulin B, Hui S, Arrhenius G. Mineral induced formation of sugar phosphates. ORIGINS LIFE EVOL B 1995; 25:297-334. [PMID: 11536701 DOI: 10.1007/bf01581773] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glycolaldehyde phosphate, sorbed from highly dilute, weakly alkaline solution into the interlayer of common expanding sheet structure metal hydroxide minerals, condenses extensively to racemic aldotetrose-2,4-diphosphates and aldohexose-2,4,6-triphosphates. The reaction proceeds mainly through racemic erythrose-2,4-phosphate, and terminates with a large fraction of racemic altrose-2,4,6-phosphate. In the absence of an inductive mineral phase, no detectable homogeneous reaction takes place in the concentration- and pH range used. The reactant glycolaldehyde phosphate is practically completely sorbed within an hour from solutions with concentrations as low as 50 micrometers; the half-time for conversion to hexose phosphates is of the order of two days at room temperature and pH 9.5. Total production of sugar phosphates in the mineral interlayer is largely independent of the glycolaldehyde phosphate concentration in the external solution, but is determined by the total amount of GAP offered for sorption up to the capacity of the mineral. In the presence of equimolar amounts of rac-glyceraldehyde-2-phosphate, but under otherwise similar conditions, aldopentose-2,4,-diphosphates also form, but only as a small fraction of the hexose-2,4,6-phosphates.
Collapse
Affiliation(s)
- S Pitsch
- Laboratorium für Organische Chemie, ETH-Zentrum, Switzerland
| | | | | | | | | |
Collapse
|
164
|
Kotkar D, Thakkar NV. Hydrogenation of olefins on Ru/pillared montmorillonite. J CHEM SCI 1995. [DOI: 10.1007/bf02841436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
165
|
|
166
|
Garrel C, Lafond JL, Guiraud P, Faure P, Favier A. Induction of production of nitric oxide in microglial cells by insoluble form of aluminium. Ann N Y Acad Sci 1994; 738:455-61. [PMID: 7832456 DOI: 10.1111/j.1749-6632.1994.tb21837.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- C Garrel
- Laboratoire de Biochimie des Micronutriments, CHRU A. Michallon, Grenoble, France
| | | | | | | | | |
Collapse
|
167
|
Sharma GVM, Ramanaiah KCV, Krishnudu K. Clay montmorillonite in carbohydrates: Use of ‘claysil’ as an efficient heterogenous catalyst for the intramolecular Ferrier reactions leading to 1,6-anhydro rare saccharides. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s0957-4166(00)86263-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
168
|
Grice ME, Murray JS, Politzer P. Calculated surface electrostatic potentials of molecular sieve models containing SiO4, AlO4, and PO4 units. JOURNAL OF MOLECULAR GRAPHICS 1994; 12:169-71, 193. [PMID: 7819157 DOI: 10.1016/0263-7855(94)80083-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Surface electrostatic potentials have been computed at the ab initio HF/STO-5G* level for two model systems: a fragment of a zeolite channel wall; and a fragment composed of SiO4, AlO4 and PO4 units. The potential above the SiO4 network is negative everywhere, despite these units commonly being regarded as electrically neutral. In marked contrast, the AlO4 and PO4 units introduce strongly negative and positive regions, respectively, giving rise to a much more heterogeneous surface potential.
Collapse
Affiliation(s)
- M E Grice
- Department of Chemistry, University of New Orleans, LA
| | | | | |
Collapse
|
169
|
Use of Montmorillonite clay for the synthesis of linear tetrapyrroles and their cyclization to Uroporphyrinogens. Tetrahedron Lett 1994. [DOI: 10.1016/s0040-4039(00)60710-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
170
|
Photoinduced electron transfer reactions of [Ru(bpy)3]2+ adsorbed onto Nafion® and clay coated electrodes in the presence of Fe3+ ions. J Electroanal Chem (Lausanne) 1994. [DOI: 10.1016/0022-0728(93)03035-n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
171
|
Gobi KV, Ramaraj R. Photoelectrochemical and quenching studies of tris(2,2′-bipyridine)ruthenium(II) bound to Nafion- and clay-coated electrodes. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/dt9940002445] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
172
|
Sabu KR, Sukumar R, Lalithambika M. Acidic Properties and Catalytic Activity of Natural Kaolinitic Clays for Friedel–Crafts Alkylation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1993. [DOI: 10.1246/bcsj.66.3535] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
173
|
Electron transfer reactions at Nafion and clay adsorbed Ru (bpy)2+3 coated electrodes. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/0304-5102(93)85051-t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
174
|
Onaka M, Hosokawa Y, Higuchi K, Izumi Y. Acidity comparison between ion-exchanged clay montmorillonites by using silylation of alcohol. Tetrahedron Lett 1993. [DOI: 10.1016/s0040-4039(00)77519-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
175
|
Kantam M, Santhi P, Siddiqui M. Montmorillonite catalyzed dehydration of tertiary alcohols to olefins. Tetrahedron Lett 1993. [DOI: 10.1016/s0040-4039(00)77523-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
176
|
Sieskind O, Albrecht P. Synthesis of alkylbenzenes by Friedel-Crafts reactions catalysed by K10-montmorillonite. Tetrahedron Lett 1993. [DOI: 10.1016/s0040-4039(00)77527-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
177
|
|
178
|
Crocker M, Herold RHM, Emeis CA, Krijger M. Preparation of acidic forms of montmorillonite clay via solid-state ion-exchange reactions. Catal Letters 1992. [DOI: 10.1007/bf00769156] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
179
|
|
180
|
Crocker M, Herold R. Carbomethoxylation of ethylene catalysed by Pd(II) complexes intercalated in smectite clay. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0304-5102(91)80162-v] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
181
|
Choudary BM, Valli VLK, Prasad AD. A Novel Montmorillonite - KMnO4System for the Oxidation of Alkenes Under Triphase Conditions. SYNTHETIC COMMUN 1991. [DOI: 10.1080/00397919108019806] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
182
|
Lenarda M, Ganzerla R, Enzo S, Storaro L. Chemistry of [Ru3O2(NH3)14]Cl6 (ruthenium red) intercalated in a smectite clay: thermal behaviour, reactivity with CO and CO/H2, catalytic activity. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0304-5102(91)80041-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
183
|
Evans PH, Klinowski J, Yano E. Cephaloconiosis: a free radical perspective on the proposed particulate-induced etiopathogenesis of Alzheimer's dementia and related disorders. Med Hypotheses 1991; 34:209-19. [PMID: 2062255 DOI: 10.1016/0306-9877(91)90213-i] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
By analogy to the etiology of the pneumoconioses, exogenous dust-induced diseases of the lung, and endogenous crystal-induced arthropathies such as gout, it is proposed that Alzheimer's dementia and allied disorders are causally related to the accumulation of fibriform inorganic deposits within the brain. Hence the neonosological term 'Cephaloconiosis'. It is proposed that: 1) either by the extrinsic migration or intrinsic formation and deposition of insoluble and persistent inorganic reactive nidi, the particle-induced generation of tissue-damaging free-radical oxygen metabolites by stimulated brain glial macrophage-type and allied phagocytic cells, provides a rationale for the etiopathogenesis of neurodegenerative processes; 2) the modulation of the injurious oxidative metabolic reaction by micronutrient and pharmacological antioxidant agents is a rational and potentially feasible strategy for future therapeutic clinical investigations.
Collapse
Affiliation(s)
- P H Evans
- MRC Dunn Nutrition Unit, Cambridge, UK
| | | | | |
Collapse
|
184
|
Solids For Catalysis and Control in Organic Synthesis. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/s0167-2991(08)61107-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
185
|
Cai ZX, Mahanti SD, Solin SA, Pinnavaia TJ. Dual percolation threshold in two-dimensional microporous media. PHYSICAL REVIEW. B, CONDENSED MATTER 1990; 42:6636-6641. [PMID: 9994751 DOI: 10.1103/physrevb.42.6636] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
|
186
|
Collet C, Delville A, Laszlo P. Steuerung der Aren-Nitrierung durch Tonminerale. Angew Chem Int Ed Engl 1990. [DOI: 10.1002/ange.19901020519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
187
|
Trost BM, Edstrom ED. Synthese von (+)-Phyllanthocin über eine metallkatalysierte Cycloreduktion. Angew Chem Int Ed Engl 1990. [DOI: 10.1002/ange.19901020509] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
188
|
Sahimi M. Diffusion, adsorption, and reaction in pillared clays. I. Rod‐like molecules in a regular pore space. J Chem Phys 1990. [DOI: 10.1063/1.458544] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
189
|
Abstract
An open-ended system of differential equations is formulated for the number of polymers of length n, n = 1,2,..., under the assumption that all monomers are kinetically equivalent. Although this assumption does not hold in real systems, solutions to the model could provide insights into the processes of polycondensation including polymerizing proteins and polynucleotides. In this paper the equilibrium solution to the system is derived analytically and is used to estimate the concentration of monomers required to obtain a fixed proportion of polymers longer than a given length. Simulation results are also presented to indicate the effects that autocatalytic interactions may have on the dynamics of polycondensation. The results suggest that relatively long-chained peptides (one to several hundred units long) could well have been synthesized under non-template or prebiotic conditions.
Collapse
Affiliation(s)
- W M Getz
- Department of Entomology, University of California, Berkeley 94720
| |
Collapse
|
190
|
Electrochemistry of dye- and surfactant-incorporated montmorillonite-modified electrodes. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/0166-6622(90)80090-q] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
191
|
|
192
|
Kennedy TP, Dodson R, Rao NV, Ky H, Hopkins C, Baser M, Tolley E, Hoidal JR. Dusts causing pneumoconiosis generate .OH and produce hemolysis by acting as Fenton catalysts. Arch Biochem Biophys 1989; 269:359-64. [PMID: 2537062 DOI: 10.1016/0003-9861(89)90118-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Silicates causing pneumoconiosis function as Fenton catalysts to generate hydroxyl radicals (.OH) when incubated with hydrogen peroxide and a reducing substance. In contrast, silicates which do not cause pneumoconiosis demonstrate no Fenton activity. Catalytic activity is decreased by pretreatment of silicates with the iron chelators deferoxamine or transferrin. Hemolysis from silicates is decreased by interventions which remove superoxide anion or hydrogen peroxide from the medium, or by pretreatment of dusts with iron chelators. Thus, asbestos and nonfibrous silicates may cause pneumoconiosis through a common oxidant mechanism by catalyzing production of toxic .OH radicals in the lung.
Collapse
Affiliation(s)
- T P Kennedy
- Pulmonary Division, University of Tennessee, Memphis 38163
| | | | | | | | | | | | | | | |
Collapse
|
193
|
Laszlo P, Vandormael J. Regioselective Nitration of Aromatic Hydrocarbons by Metallic Nitrates on the K10 Montmorillonite under Menke Conditions. CHEM LETT 1988. [DOI: 10.1246/cl.1988.1843] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
194
|
Cornelis A, Gerstmans A, Laszlo P. Regioselective Liquid-Phase Toluene Nitration with Modified Clays as Catalysts. CHEM LETT 1988. [DOI: 10.1246/cl.1988.1839] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
195
|
Choudary B, Mukkanti K, Rao Y. New interlamellar montmorillonitesilylphosphinepalladium(ii) complex for stereo and shape selective hydrogenation of alkynes. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/0304-5102(88)85001-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
196
|
Jin W, Mahanti SD. Theory of interlayer spacing in ternary graphite intercalation compounds. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 37:8647-8655. [PMID: 9944226 DOI: 10.1103/physrevb.37.8647] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
197
|
|
198
|
Collins JR, Loew GH, Luke BT, White DH. Theoretical investigation of the role of clay edges in prebiotic peptide bond formation. II. Structures and thermodynamics of the activated complex species. ORIGINS LIFE EVOL B 1988; 18:107-19. [PMID: 3368213 DOI: 10.1007/bf01808785] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Amino acid activation by anhydride formation in model tetrahedral silicate and aluminate sites in clays and neutral phosphates have been studied by semi-empirical molecular orbital calculations. The results have been compared to previous ab initio studies on the reactant species and were found to be in good agreement. The geometries of all species were totally optimized and heats of formation obtained. Relative heats of formation of the anhydrides indicate the extent of anhydride formation to be A1 greater than Si greater than P which is the same order as the stability of hydrolysis. The relative efficacy of the anhydrides in promoting peptide bond formation has been evaluated using both thermodynamic and chemical reactivity criteria. Heats of reaction for model reactions were calculated from calculated enthalpies of formation of the products and reactants. The electrophilicity of the carbonyl carbon and the nucleophilicity of the oxygen were specifically used as indicators of chemical reactivity towards dipeptide formation by the activated amino acids. Our results indicate that if the reaction mechanism is dominated by the nucleophilic character of the oxygen, tetrahedral A1 sites should be more active than Si, and if the electrophilic character dominates, the order would be reversed.
Collapse
Affiliation(s)
- J R Collins
- Molecular Research Institute, Palo Alto, CA 94303
| | | | | | | |
Collapse
|
199
|
Schoen M, Cushman JH, Diestler DJ, Rhykerd CL. Fluids in micropores. II. Self‐diffusion in a simple classical fluid in a slit pore. J Chem Phys 1988. [DOI: 10.1063/1.454211] [Citation(s) in RCA: 150] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
200
|
|