Vol 4, No 1

Table of Contents


Hamaker Coefficient Concept: The Application to the Mycobacterium Tuberculosis – Macrophage Interactions Mechanism PDF
J. L. Chukwuneke, P. C. Chukwuneke, P. C. Okolie, J. E. Sinebe
M-Tb – macrophage interactions were studied using the Hamaker coefficient concept as a surface energetics tool in determining the interaction processes, with the surface interfacial energies explained using van der Waals concept of particle – particle interactions. Using the previous works that established the role of surface thermodynamics in various processes from the balanced electrostatic repulsion, and the van der waals attraction mechanism, that the concept of attraction or repulsion between the interacting particles were modeled. The Lifshitz derivations for van der Waals forces were applied as an alternative to the contact angle approach which has been widely used in other biological systems. The methodology involved sputum sample collection, mycobacterium and macrophages structural studies, and the study of the mechanism of interaction of the bacterium and macrophage. Twenty samples each of infected, uninfected and M-Tb/HIV co-infected sputum were collected and screened using GeneXpert and Ziehl-Neelsen staining method. The absorbance, ā, values of each specimen, for wavelength range of 230-950nm were measured using digital Ultraviolet Visible Spectrophotometer.Matlab software tools were used in the mathematical analysis of the data generated from the absorbance values.The Hamaker constantsand the combined Hamaker coefficientA132were obtained. The values of A132abs = 0.21631x10-21Joule (M-Tb infected sputum) and Ã132abs = 0.18825x10-21Joule (M-Tb/HIV co-infected sputum) were obtained for M-Tb/HIV – infected macrophage. The implication of this result is the positive value of the absolute combined Hamaker coefficient which entails net positive van der waals forces demonstrating an attraction between M-Tb and the macrophage. This however, implies that infection is very likely to occur. It was also shown that in the presence of HIV, the interaction energy is reduced by 13% confirming adverse effects observed in HIV patients suffering from tuberculosis. Negative Hamaker coefficient (-0.22669x10-19mJ/m2) indicated that isolation of M-Tb is realistic. The desired outcome is that the bacteria do not adhere to the macrophage to avoid bacteria penetrating it, in which case a condition for rendering combined Hamaker coefficient negative is required. Thus, condition was sought for repulsion to occur and that condition was based on the value of A33 that would render the absolute combined Hamaker coefficient A132abs negative. Mathematically it was derived as A33≥0.9527x10-21Joule which satisfies this condition for negative A132abs. To achieve the condition of A33 above, possible additive(s) in form of drugs to the sputum should be required.

Expression of α-Amylase in a Tropical Strain Penicillium rubrum with Bread as Growth Substrate PDF
Adekunle Odunayo Adejuwon, Anthonia Olufunke Oluduro, Femi Kayode Agboola, Patrick Ojo Olutiola, Melissa Jane Robbiani, Sheldon Jerome Segal
Background: Penicillium rubrum is an Ascomycete known to produce the toxic metabolites rubratoxins A and B associated with jaundice and convulsions in infected patients. The fungus is known to contaminate grains and grain products in the tropics. Materials and methods: In this current investigation, sterile fresh bread was inoculated with spore suspensions of approximately 6 x 105 spores of isolate per ml of a tropical strain Penicillium rubrum. Incubation was at 25oC. Extracellular proteins produced were subjected to partial purification by ammonium sulphate precipitation and dialysis. Further purification using gel permeation and ion-exchange chromatography was employed. Results: The proteins produced by Penicillium rubrum in the inoculated medium exhibited α-amylase activity. The molecular weights of the α-amylase fractions obtained and estimated by gel filtration using Sephadex G-100 were approximately 47, 316 Daltons and 15, 849 Daltons. The apparent Michalis-Menten constant (Km) values for the hydrolysis of starch by the purified α-amylase fractions were approximately 10 mg/ml, 5 mg/ml, 25 mg/ml and 16 mg/ml. Optimum activities were at 35oC for all the fractions and were at pH 6.0. The activities of the α-amylase fractions produced by the fungus were stimulated at varying degrees by NaCl, KCl, CaCl2and MgCl2but inhibited by ethylene diamine tetraacetic acid (EDTA), mercuric chloride (HgCl2) and 2,4-dinitrophenol (DNP). The α-amylase fractions were sensitive to heat, losing all their activities within twenty minutes of heating at 80oC. Conclusion: Apart from the toxic metabolites rubratoxins produced by Penillium rubrum, the fungus produces α-amylases in contaminated bread at 25oC in the tropics. These α-amylases are stable at 35oC and at pH 6.0.

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