A Simple Confidence Band for the Michaelis-Menten Equation

Open access journalAnalysis of enzyme kinetic data requires more than just comparisons of Kms and Vmaxs using the corresponding error estimates of the parameters. This approach is often employed, but it can prompt contradictory and misleading inferences that might be avoided using a confidence band. We derive expressions for the confidence band for the Michaelis-Menten rate equation that rely on estimates and variances of Km and Vmax. These can be expressed in terms of the substrate concentration or the rate of reaction. While these equations are simple, they are nonlinear, which reinforces the need to consider both parameters simultaneously. The equations show that the amplitude of the confidence interval () passes through a maximum if the variance of the Km is sufficently large compared with the variance of Vmax. We illustrate the value of the expressions by applying them to comparisons of the kinetics of enzymes involved in nitrogen metabolism in parasites. These examples confirm that (i) the variance of the estimate of the Km has a particularly significant effect on and (ii) comparisons among Kms and among Vmaxs are not necessarily sufficient to determine the significance of differences in activity

What Happens When the Wrong Equation is Fitted to Data?

Open access JournalA common variant of the Michaelis-Menten model of enzyme kinetics involves inhibition by excess substrate. This phenomenon is known as substrate inhibition and the mathematical description of it requires an inhibition constant (Ki) as well as the usual kinetic parameters (Km and Vmax). Fitting the 3-parameter substrate inhibition expression to data that might reasonably be described by the 2-parameter Michaelis-Menten model yields biased estimates of Km and Vmax. Numerical simulations demonstrate that the extent of the bias is related to the magnitude of the estimated Ki. The quality of the data is particularly important in determining the size of Ki and, therefore, in the bias of the other parameters. Consideration of the residuals, statistical justification of the inclusion of extra parameters and reporting of the estimated values should be matters of routine. The estimates of Km and Vmax obtained from a three-parameter substrate inhibition model can only be compared with the corresponding estimates from the two-parameter Michaelis-Menten model with caution

The Role of Antioxidant Hesperidin in the Attenuation of Lung Cancer Caused by Benzo[a]pyrene in Balb/c Mice

It was postulated that chemoprevention is one of the most promising and realistic approaches in the prevention of cancer. Hesperidin (HDN) is one such naturally occurring flavonoid widely found in citrus fruits. The aim of the present study is to divulge the chemopreventive nature of HDN during benzo[a]pyrene (b[a]p) induced lung cancer in BALB/c mice. Administration of b[a]p (60 mg/kg body weight) to mice resulted in increased lipid peroxidation (LPO), lung specific tumor marker carcinoembryonic antigen (CEA) and serum marker enzymes aryl hydrocarbon hydroxylase (AHH), alanine transaminase (ALT), with concomitant decrease in the levels of tissue antioxidants like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione. HDN supplementation (25 mg/kg body weight) significantly attenuated these alterations thereby showing potent anticancer effect in lung cancer. Overall, these findings substantiate the chemoprotective potential of HDN against chemically-induced lung cancer in BALB/c mice

A Review On Heliotropium Indicum L. (Boraginaceae)

Heliotropium indicum Linn., commonly known as ‘Indian heliotrope’ is very common in India with a long history of traditional medicinal uses in many countries in the world. The plant is reported to possess antibacterial, antitumor, uterine stimulant effect, antifertility, wound healing, anti-inflammatory, antinociceptive and diuretic activities. Several pyrrolizidine alkaloids have been isolated from this species. The active principle Indicine-N-oxide has reached Phase 1 clinical trials in advanced cancer patients. But severe toxic side-effects showed that a therapy with indicine-N-oxide was not justified. Most of the alkaloids are hepatoxic and therefore internal use of Heliotropium species is not recommended. External application to promote wound healing and to fight infections seems to be less hazardous, but more research is needed. The comprehensive account of the chemical constituents and the biological activities are presented in this review such that the potential use of this plant in various traditional medicines can be systematically evaluated

The recovery of fingerprints from fired cartridge cases : a comparison of current methods of development with an electrostatic deposition technique

A comparison of three current methods of fingerprint development on untreated metals (cyanoacrylate fuming with Brilliant Yellow 40 fluorescent dyeing, gun blue solution, and palladium deposition) and an electrostatic deposition technique is described. The conventional methods were successful to varying degrees at developing fingerprints on cartridge cases, with greater success observed when used on unfired cartridge cases. A Mann-Whitney U Test revealed no significant difference in the quality of prints developed by each of the current methods. However, the gun blue solution and the palladium deposition technique both yielded more potentially identifiable prints than the cyanoacrylate with brilliant yellow 40 technique. This work establishes that under specific circumstances, fingerprint residues and ridge detail can survive on the surface of a fired cartridge case. The electrostatic deposition technique failed to give any results using the setup described