Dipole moment in TIM alpha/beta fold proteins.

TIM proteins of alpha/beta barrel fold from alpha/beta class as given in SCOP database were taken for dipole moment analysis. In all, 32 structures were analyzed for their dipole moment contributions. Representative structures from 20 super families in the alpha/beta fold, with different enzyme functions and 12 protein domains of TIM family in TIM super family were considered. The active sites of these proteins are located on the C-terminal side of the beta-strands. The molecules of same alpha/beta fold, but differing in their functionality also showed a common electrostatic field pattern along the barrel axis and had the dipole moment along the barrel axis and towards C-terminal end of the beta-strands. However, it is observed from our calculations that the dipole moment direction is possibly a consequence of the structural fold, with distribution of charges playing a modulatory role, and does not contribute to the location of active site. We show here that apart from the commonly held view as proposed by Hol et al [Hol W G L, van Duijnen PT and Berendsen H J C (1978) Nature (London), 273, 443-446] of the role of the alpha helical dipole moment, the beta-sheets in the barrel can also have a considerable dipole moment contribution. Taken together with our dipole moment analysis on integral membrane proteins [Vasanthi G and Krishnaswamy S (2002) Indian J Biochem Biophys 39, 93-100], this suggests the need to examine the role of dipole moment in the case of especially beta sheets forming barrels.

Dipole moment analysis of membrane proteins suggests role in orientation in the membrane.

The position independent dipole membrane proteins need to be oriented in the membrane in order to function as channels, transporters or recognition systems. Membrane proteins can be broadly classified as either predominantly alpha helical or beta barrel in nature. All the different types of thirteen beta barrel membrane proteins (2OMF, 2POR, 1PRN, 1PHO, 1IIV, 1AF6, 1AOT, 2MPR, 1OSM, 1QJ8, 1BXW, 2FCP and 1FEP) and six alpha helical membrane proteins (1BL8, 1MSL, 1QLB, 1AR1, 1PSS and 1QHJ) from the Protein Data Bank were analyzed. Dipole moment was calculated for both classes of proteins. In all the oligomers, the orientation of the dipole was found to be parallel to direction of insertion that is perpendicular to the possible membrane layer. Monomers do not show a similar orientation. In all the alpha helical oligomers, the dipole points from the intra-cellular to the extra-cellular side. In the oligomeric beta barrel proteins, the direction of the dipole is from the extra-cellular to the intra-cellular side, except for OmpF from E.coli, Omp36 from Klebsiella pneumonia and LamB from E.coli where the situation is reversed. However, the dipole moments of the monomeric proteins and the monomers of the oligomers themselves are not oriented parallel to the molecular axis and the insertion orientation, but they are almost parallel to the membrane surface. It is possible that the quaternary oligomeric association is necessary for the correct orientation in the membrane and this is aided by the dipole orientation. The electrostatic potential surface calculated with all atoms, which also do not show clear separation of charge surfaces. Calculations suggest that backbone structure and oligomer are sufficient for providing the dipole orientation.

Iron nutritional status of adolescent girls from rural area and urban slum.

Iron nutritional status of adolescent girls belonging to an urban slum and rural areas was assessed by measuring serum ferritin levels. Overall anemia was observed in 25% of the girls irrespective of their urban rural residence. A higher percentage of rural girls (37.5%) especially below the age of 12 years showed evidence of anemia. Thereafter, the prevalence was similar in both urban and rural girls who had not attained menarche. With increasing age, urban girls who had attained menarche showed an increase in the prevalence of anemia. The prevalence of iron deficiency (serum ferritin < 12 micrograms/dl) showed a progressive increase from 60% at < 12 to 28% at > 14 yrs especially in the girls not attained menarche in the girls not attained menarche in the rural area. Overall iron deficiency was of much higher order in the rural girls irrespective of the menarcheal status. Distribution of iron/folate tablets to cover girl population may go a long way to correct the anemia and iron deficiency in the vulnerable groups.

Plasma ferritin in the assessment of iron status of Indian infants.

In order to assess the iron nutritional status of infants, plasma ferritin levels were measured in the infants and children at different time intervals till two years of age from two different socio economic groups. While ferritin levels at 3-4 months age were significantly higher in upper income group infants, levels were almost similar in the subsequent infancy between the two income groups. A close correlation was seen between ferritin levels of mothers and infants at 1-3 months of age (p less than 0.001). Prenatal iron supplements (oral or parenteral) resulted in higher ferritin levels at 4-6 months age as compared to placebo group. While the infants born to mothers receiving parenteral iron did not show any evidence of iron deficiency (serum ferritin levels less than 12 ng/ml), 23.5 and 25.0% of infants in oral iron and placebo group had evidence of iron deficiency between 6-12 months. Thus it would appear that improving the iron status of mothers during pregnancy will have significant impact on the iron status of breast fed infants till 6 months.

Use of body mass index for assessing the growth status of infants.

Growth status of infants measured by weight and height was assessed from birth to 12 months in a randomly selected community from the urban slums of Hyderabad City. Mean birth weight was 2.82 kg. Weight/height indicator of body mass index (BMI) showed a progressive increase till 4th month, followed by more or less a constant figure with a mean value of 1.50 in longitudinal, semi-longitudinal and cross sectional data till one year. Critical limit for BMI at birth for given weight of 2.5 kg was 1.20 and subsequently increased to 1.35. BMI was well correlated with weight and weight for height (%) and least correlated with height. Children with height of 90% or above and birth weight of above 2.5 kg were observed with better growth and better maintenance of weight for height (%) and BMI till 6 months.