Biomedical subjects

Srinivas Janaswamy

Publications and source records attributed to Srinivas Janaswamy.

6 recordsLinked to original sources

PubMed2006

Development of a low glycemic maize starch: preparation and characterization.

A low glycemic index starch was developed by partial alpha-amylase treatment, and its fine structure responsible for slowly digestible and resistant properties was investigated. Different digestion rates were obtained for gelatinized, retrograded starch by varying the enzyme dosage and reaction time. Analysis by high performance size-exclusion chromatography (HPSEC) coupled with multiangle laser-light scattering indicated that the molecular weighs of amylopectin and amylose were reduced during the digestion, to less than 100 kDa. A debranched chain length study using high performance anion-exchange chromatography equipped with an amyloglucosidase reactor and a pulsed amperometric detector and HPSEC revealed that short chains of amylopectin and noncrystalline amylose were rapidly digested, while DPn 121 chains showed resistance, followed by DPn 46 chains. X-ray diffraction analysis revealed that the crystalline structure in the treated starches survived cooking. These starches not only have slowly digestible and resistant character, but also retain some branched structure for adequate functionality.

Administration, Oral↗

PubMed2005

Polysaccharide structures from powder diffraction data: molecular models of arabinan.

X-ray intensity data from a polycrystalline sample of debranched arabinan, [-->5)-alpha-L-Ara(f)-(1-->](n), have been obtained using a powder diffractometer in order to determine its three-dimensional structure. The observed peaks index on a monoclinic cell with a=5.444(7), b=6.395(10), c=8.680(5) A, and gamma=99.6(3) degrees , V=298 A3. One 2-fold helix along the c-axis can be accommodated in the unit cell. Molecular and packing models have been analyzed using the seven C-2'-endo/C-3'-endo allomorphs originally proposed by Radha and Chandrasekaran [Carbohydr. Res. 1997, 298, 105]. The generated powder pattern matches closely with the observed diffraction only for one C-2'-endo model. In this structure, the three main chain conformation angles are in the trans domains, there are no intra-chain hydrogen bonds, and the packing arrangement is stabilized by inter-chain O-3-H...O-2 bonds.

Carbohydrate Conformation↗

PubMed2003

Acetan:glucomannan interactions--a molecular modeling study.

X-ray fiber diffraction patterns from deacylated acetan and glucomannan (konjac mannan) blends are diagnostic of good orientation and modest polycrystallinity. The meridional reflection on the sixth layer line suggests that the binary complex is a 6-fold helix of pitch 55.4 A. A molecular modeling study incorporating this information reveals that a double helix in which one strand is acetan and the other glucomannan is stereochemically feasible. While the backbone and side groups are sufficiently flexible to allow the chains to associate with the same or opposite polarity, the parallel model is superior in terms of unit cell packing. The results are compatible with the observed synergy; namely the weak gelation behavior of the complex. The molecular model can be generalized for the binary system when acetan is replaced by xanthan or glucomannan by galactomannan.

Acetylation↗

PubMed2002

Morphology of Western larch arabinogalactan.

A molecular modeling study has revealed that (1 --> 3)-beta-D-galactan can not only adopt a triple helical structure similar to that of the corresponding glucan but can also accommodate a highly flexible beta-D-Gal-(1 --> 6)-beta-D-Gal disaccharide moiety as a side group 6-linked to every galactosyl unit in the main chain. The resulting triple helix, applicable to Western larch arabinogalactan, can assume quite different morphologies since the side group has access to several allowed conformational states. Some of the preferred modes of association between these helices have been visualized using preliminary X-ray fiber diffraction data.

Carbohydrate Conformation↗

PubMed2002

Effect of calcium ions on the organization of iota-carrageenan helices: an X-ray investigation.

X-ray fiber diffraction analysis confirms that calcium iota-carrageenan forms a threefold, right-handed, half-staggered, parallel, double helix of pitch 26.42 A stabilized by interchain hydrogen bonds. According to the detailed structural results, three helices are packed in a trigonal unit cell (a=23.61 and c=13.21 A). Strong interactions between the sulfate groups of neighboring helices, mediated by calcium ions and water molecules, are responsible for stabilizing the three-dimensional structure.

Calcium↗

PubMedDate not supplied

Role of the pericarp cellulose matrix as a moisture barrier in microwaveable popcorn.

Since moisture loss of popcorn can cause an increase in the number of unpopped kernels, pericarp properties of popcorn hybrids were analyzed to understand factors affecting moisture loss rate during microwave heating. Differential scanning calorimetry profiles of ground pericarp displayed a notable exothermal event, and hybrids with superior microwave popping performance (fewer unpopped kernels) exhibited significantly higher enthalpies. The number of unpopped kernels was highly correlated (r = 0.826, p = 0.011) with pericarp enthalpy values. X-ray analysis confirmed that cellulose and arabinoxylan are the major structural components of the pericarp. Structural changes in cellulose were induced by moisture and heat, and considerable enhancement in crystallinity occurred when the pericarp was heated in the presence of water. Results of this study indicate that the cellulose component of the pericarp is responsible for the development of exothermal events and increased crystallinity. Thus, the propensity of cellulose to form crystalline structures in the popcorn pericarp during microwave heating improves moisture retention and hence popping performance.

Cellulose↗