Spectroscopic (UV-VIS and IR) and computational (hyperchem) studies on the molecular structure of synthetic melanoidin

Date

4-2000

Degree

Bachelor of Science in Agricultural Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ernesto J Del Rosario

Co-adviser

Evamarie P. Capareda

Abstract

Equimolar amounts of glycine and glucose were used to prepare a structurally simple melanoidin polymer. Gel filtration chromatography showed that this polymer has a wide molecular weight distribution range. By using protein standards, its approximate molecular weight was found to be 17.4 kDa. IR spectral analysis indicated the presence of carboxylate, conjugated C=C and C=N, and 0-H groups. The maximum UV absorbance in water occurred at 290 nm with molar extinction coefficient of about 125,000. Probable monomeric structures proposed by different researchers were evaluated using HyperChem 5.0 software. All probable structures underwent geometry optimization using the semiempirical PM3 method before they were subjected to a specific calculation. For UV-VIS spectral calculation, melanoidin monomers were further truncated to contain the conjugated sections. This resulted in twelve structures from which UV3a, UV4b, and UV7 were chosen to be the dominant chromophores responsible for the transition appearing at 290nm. For IR spectral calculation, six probable monomeric structures were studied. IR4 approximated the experimental IR spectrum with due consideration of the software's limitation. The structure is similar to that proposed by Cammerer and Kroh (1994). The difference is in the presence of carboxylate in the C6 of the sugar moiety instead of a carbinol group. Electrophoretic data showed a net negative charge for the polymer.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2000 A13 M36

Document Type

Thesis

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