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Molecular orbital studies on nucleoside antibiotics X. Conformation of nebularine and isoguanosine (1993)

Saran, A. ; Patnaik, L. N.

Springer

Theoretical chemistry accounts 85 (1993), S. 17-26

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ISSN: 1432-2234

Keywords: Nebularine ; Isoguanosine ; Crotonoside ; PCILO ; Conformation ; Nucleoside antibiotics

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Summary Conformational properties of two nucleoside analogs, namely nebularine and isoguanosine have been investigated by using PCILO (Perturbative Configuration Interaction using Localized Orbitals) method. Nebularine (9-β-ribofurnosyl purine) is a naturally occurring purine nucleoside which is structurally similar to adenosine and it inhibits the growth of tumor cells and influenza B virus. Isoguanosine is one of the two naturally occurring analogs of guanosine. Both C2′-endo and C3′-endo sugar puckerings have been considered for both the molecules with preselected values of torsion angles around C2′–O2′ and C5′–O5′ bonds. The results indicate that nebularine has conformational preferences very similar to those of its parent nucleoside, adenosine; whereas the conformational properties of isoguanosine are very different from those of guanosine as well as adenosine. The important implications of these results have been discussed in terms of the biological activity of these molecules.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01374573

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Effect of structure and composition on physico-mechanical properties of methyl methacrylate/alkyl (meth)acrylate copolymers (1993)

Patnaik, M. ; Choudhary, V. ; Varma, I. K. ; [et al.]

Weinheim : Wiley-Blackwell

Angewandte Makromolekulare Chemie 205 (1993), S. 47-58

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ISSN: 0003-3146

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Description / Table of Contents: Methylmethacrylat (MMA) mit einem Prepolymergehalt von 6-8% wurde mit unterschiedlichen Anteilen (1-20%) 2-Ethylhexylmethacrylat (EMMA), n-Hexylmethacrylat (HMA), 2-Ethylhexylacrylat (EHA) oder n-Hexylacrylat (HA) copolymerisiert. Aus den erhaltenen Copolymeren wurden Folien hergestellt, an denen der Einfluß der Copolymerstruktur auf Lichtdurchlässigkeit, Dichte und mechanische Eigenschaften ermittelt wurde. zugsfestigkeit and Speichermodul nahmen mit zunehmendem Comonomergehalt ab. Die Dehnung stieg im Fall von MMA/EHA- und MMA/HA-Copolymerfolien mit 15 und 20 Gew.-% Comonomeranteil merklich an. Mittels DMTA wurde die Erweichungstemperatur der Copolymeren bestimmt. Die HDT und die Erweichungstemperatur nahmen unter Biegebelastung mit steigendem Comonomergehalt de Copolymeren ab.

Notes: The paper describes the fabrication of cast acrylic sheets by copolymerizing a prepolymer syrup of methyl methacrylate (MMA) with varying amounts (1-20 wt.-%) of 2-ethylhexyl methacrylate (EHMA), n-hexyl methacrylate (HMA), 2-ethylhexyl acrylate (EHA) and n-hexyl acrylate (HA). The effect of structure of copolymer on light transmittance, density and mechanical properties was evaluated. Tensile strength and storage modulus decreased with increasing comonomer content. Strain increased significantly in the case of MMA/EHA and MMA/HA copolymer sheets having 15 and 20 wt.-% of comonomer. Softening temperature of copolymer samples was determined using dynamic mechanical thermal analysis. Heat deflection temperature under flexural load and softening temperature decreased with increasing comonomer content in copolymer.

Additional Material: 3 Ill.