2,448 research outputs found
Entropy and biological systems: experimentally-investigated entropy-driven stacking of plant photosynthetic membranes
According to the Second Law of thermodynamics, an overall increase of entropy contributes to the driving force for any physicochemical process, but entropy has seldom been investigated in biological systems. Here, for the first time, we apply Isothermal Titration Calorimetry (ITC) to investigate the Mg21-induced spontaneous stacking of photosynthetic membranes isolated from spinach leaves. After subtracting a large endothermic interaction of MgCl2 with membranes, unrelated to stacking, we demonstrate that the enthalpy
change (heat change at constant pressure) is zero or marginally positive or negative. This first direct experimental evidence strongly suggests that an entropy increase significantly drives membrane stacking in
this ordered biological structure. Possible mechanisms for the entropy increase include: (i) the attraction between discrete oppositely-charged areas, releasing counterions; (ii) the release of loosely-bound water molecules from the inter-membrane gap; (iii) the increased orientational freedom of previously-aligned
water dipoles; and (iv) the lateral rearrangement of membrane components.This work was supported consecutively by Australian Research Council grants (DP0664719 and DP 1093927)
Pediatric Obesity in Primary Care
The purpose of this evidence-based quantitative quasi-experimental research was to compare if providing the parents with information on the health risk associated with childhood obesity would cause the parents to make healthier food choices and encourage their children to be involved in a full hour of physical activity a day. Participants included parents and pediatric and adolescent children 5 to 18 years of age at a solo practice primary care office in a large city in Southern, California, which specializes in treating pediatric and adolescent patients. A pre- and postquantitative intervention design were used and analyzed using the paired t test. The educational intervention on childhood obesity had a significant effect on the pre- and postintervention mean scores for the General Nutrition Knowledge Questionnaire. The preintervention mean score was 45.40, and the postintervention mean score was 51.20, which showed clinical significance with a (p = \u3c .001). The participants’ demographics, age, weight, height, ethnicity, body mass index (BMI), and BMI percentage were analyzed using descriptive statistics. The sample size included participants (N = 54), females (n = 28), and males (n = 26). Considerations for future research may include providing parents with more resources to obtain healthier food choices to prevent childhood obesity, such as a social worker for families who lack financial resources for healthy food choices, a dietician to assist families with meal planning, and community resources for daily physical activity
Recommended from our members
Fructose and the Maillard reaction
It is widely accepted that the Maillard reaction, specifically the development of Advanced Glycation End-products (AGEs) in vivo, is linked to the pathogenesis of diabetic secondary complications. The same diseases that occur in old age are similarly thought to develop as a function of the accumulation of AGEs. This thesis presents an in vitro investigation into glycation by fructose (fructation) and discusses the potential for in vivo fructation. The contribution of in vivo fructation to degenerative diseases is unknown, largely because assays for glycation underestimate, or do not detect, fructation (Ahmed N& Furth A. J. 1992, Clin. Chem. X8,1301-1303).
In vitro radiolabelling illustrates that incorporation of fructose into protein, through the Maillard reaction, is more swift than glucose. The development of AGE-fluorescence reflects the incorporation of the two sugars, i. e. higher upon fructation.
A novel colorimetric assay for glycation (including fructation), based on the reaction of 2,4-dinitrophenylhydrazine (DNPH) with protein-bound carbonyl groups, is presented. The DNPH assay detects compounds that are intermediates in post-Amadori, or post-Heyns reactions, and precede development of fluorescence. The production of the protein-bound carbonyl intermediates is largely dependent on the presence of lipid and free metal. The same group of compounds are probably the principle site of action of aminoguanidine, which blocks the production of AGEs.
An in vitro model is presented, to show how protein glycated in one part of the body, can long after maintenance of euglycaemia, become covalently cross-linked to a second protein. Lysozyme was glycated with low concentrations of fructose, or using short periods of fructation, and the free fructose removed. The fructated lysozyme was subsequently incubated in sugar-free buffer with native ßlactoglobulin and produced a 32kD heterodimer of the two covalently cross-linked proteins
- …