Transition of hemoglobin between two tertiary conformations: The transition constant differs significantly for the major and minor hemoglobins of the Japanese quail (Cortunix cortunix japonica)

We demonstrate that 5,5′-dithiobis(2-nitrobenzoate) – DTNB – reacts with only CysF9[93]β and CysB5[23]β among the multiple sulfhydryl groups of the major and minor hemoglobins of the Japanese quail (Cortunix cortunix japonica). Kequ, the equilibrium constant for the reaction, does not differ very significantly between the two hemoglobins. It decreases 430-fold between pH≈5.6 and pH≈9: from a mean of 7±1 to a mean of 0.016±0.003. Quantitative analyses of the Kequ data based on published X-ray and temperature-jump evidence for a tertiary structure transition in liganded hemoglobin enable the calculation of Krt, the equilibrium constant for the r←→t tertiary structure transition. Krt differs significantly between the two hemoglobins: 0.744±0.04 for the major, 0.401±0.01 for the minor hemoglobin. The mean pKas of the two groups whose ionizations are coupled to the DTNB reaction are about the same as previously reported for mammalian hemoglobins

Tertiary conformational transition in sheep hemoglobins induced by reaction with 5,5´-dithiobis(2-nitrobenzoate) and by binding of inositol hexakisphosphate

We have determined the second-order reverse rate constant, kR, for the reaction of 5,5´-dithiobis(2- nitrobenzoate) – DTNB – with sheep hemoglobins as a function of pH from values of the second-order forward rate constant, kF, and the equilibrium constant, Kequ, at 25 °C: kR¼ kF Kequ. We demonstrate that (i) inositol hexakisphosphate (inositol-P6) decreases kF and kR by increasing Krt, the r⇌t tertiary conformation transition constant; (ii) the conformation favored for both the forward and reverse reactions is the r conformation. For stripped hemoglobin we obtain from the kF data a t isomer population of 34.6% (±14) prior to reaction with DTNB; from the kR data we calculate a t isomer population of 44.8% (±4) following reaction with DTNB. In the presence of inositol-P6 the latter value is increased to 79.5% (±2). These results demonstrate that an allosteric transition occurs on reaction with DTNB and on inositol-P6 binding

Transition of haemoglobin between two tertiary conformations: Inositol hexakisphosphate increases the transition constant and the affinity of sheep haemoglobin for 5,5′-dithiobis(2-nitrobenzoate)

The equilibrium constant (Kequ) for the reaction of 5,5′-dithiobis(2-nitrobenzoate) — DTNB — with the CysF9 [93]β sulphydryl group of the haemoglobins of the sheep decreases by about two orders of magnitude between pH≈5.6 and 9.2: from a mean of 7.2±1 to a mean of 0.044±0.01. Calculations from the pH dependence of Kequ show that in the r⇌t tertiary conformational transition of haemoglobin the t isomer population is 50.7 and 61.8% for the major and minor haemoglobins, respectively. In the presence of inositol hexakisphosphate (inositol-P6), Kequ increases for both haemoglobins by about an order of magnitude through most of the pH range. The t isomer population also increases to 82.1 and 79.6% for the major and minor haemoglobins, respectively. These results indicate that inositol-P6 increases the affinity of the sulphydryl for DTNB by increasing the population of the t isomer. It is highly probable that a minimum fourstate model that includes the r⇌t transition is required for a full understanding of haemoglobin function

Effect of cold temperature storage on the quality attributes of pawpaw and guava leathers

The effect of cold temperature storage on the quality attributes of pawpaw and guava leathers was evaluated. Pawpaw leather was significantly higher than guava leather in calorific content, water activity, pH and total mould count throughout the duration of storage. However Guava leather was higher in texture. Sensory scores in relation to period of storage showed that Guava leather gave better result in overall acceptability at zero, one and two months of storage at 8 ± 10C. Guava leather also gave better sensory qualities in fruitiness, smell, chewiness, toughness, colour, and overall acceptability when varietal influence is considered. Guava leather is better accepted. (African Journal of Biotechnology: 2002 1(2): 61-63

High ionic strength or presence of inositol hexakisphosphate reverses the unusually low pKA of CYSH3(125)Β of guinea pig haemoglobin

The kinetics of the reaction of 5,5'-dithiobis(2-nitrobenzoate) with guinea pig oxy- and carbonmonoxyhaemoglobin are biphasic. The two phases differ in rate by two orders of magnitude. For the fast phase, quantitative analysis of the pH dependence of the apparent second order rate constant, kapp, shows that it has all the characteristics associated with the reaction of CysF9(93)β, a sulphydryl group that is invariant in all mammalian haemoglobins. The slow kinetic phase is assigned to CysH3(125)β. Quantitative analysis of the pH dependence of kapp for this phase at 50 mM ionic strength gave an unusually low pKa of 6.0 for this sulphydryl group. Published data on guinea pig haemoglobin show that it has a much-enhanced acid Bohr effect compared to human haemoglobin. This indicates that CysH3(125)β functions as an acid Bohr group in guinea pig haemoglobin. Comparison with human haemoglobin indicates that this cysteine reduces the alkaline Bohr effect of guinea pig haemoglobin between pH 7 and 6, and enhances its acid Bohr effect below pH 6. From kinetic data collected at high salt concentration, and in the presence of inositol hexakisphosphate, it is shown that the pKa of the sulphydryl increases to ca 9 and 7.7, respectively. Under these conditions, CysH3(125)β ceases to be an acid Bohr group.DOI: http://dx.doi.org/10.4314/bcse.v27i1.1

Performance Evaluation of a Centrifugal Pump with different Impeller Materials

Many factors affect the performance characteristics of a pump. One of these is the impeller material. This paper is on the effect of impeller material on the operating characteristics of a centrifugal pump. The impeller materials used were cast iron, bronze and zinc. Cost, pumping efficiency, pressure head and power consumption are the factors that were taken into consideration. The results from the test, showed that the impeller made of zinc material was found to be more efficient (48.24%) and required the most power (3.38bhp). The zinc impeller was the least expensive to manufacture and pumped better head. The zinc impeller however failed at (very) high pump speed due to the fact that its strength could not match up with the pump speed. The cast iron impeller on the other hand, required the least power (0.86bhp) to run but pumped the least head (6.25m) and was more efficient (46.35%) than the bronze impeller; this was majorly due to cavitation and friction losses. The bronze impeller pump was the least efficient (38.79%), the most expensive to manufacture but pumped more head (8.50m) than the cast iron impeller and required more power (2.32bhp) than the cast iron impeller

Review of Maintenance Strategies For Achieving Sustainable Developments In Tropical Climates

Buildings, like almost all physical objects degrade over time due to a combination of factors. The deterioration affects all components and parts of the building in different ways, gradually reducing the quality of the structure and adversely impacting the building’s ability to effectively perform its basic functions in an environment. This paper relied on a systematic review of published literatures in reputable databases to examine how building developments and public environments can be designed in tropical climates to require minimal maintenance activities to enhance the ease of executing such activities. 39 open access published documents were reviewed. Data sieved from the publications were content analysed and descriptively presented in themes. The study identified principles and methods which can be implemented in the design of buildings with a focus on maintainability towards enhancing the development of sustainable public buildings and environments in tropical climates. The review promotes maintenance culture and emphasises increased consideration for maintenance in building design, which further helps to promote the eleventh target of the 17 Sustainable Development Goals that aims at the development of resilient, safe and sustainable communities, cities and human settlements. The paper is instructive to researchers, scholars, students of architecture and building design, as well as policy makers on issues surrounding the principles of designing for maintainability, particularly in tropical settings

The History of Private Sector Participation in University Education in Nigeria (1989-2012)

There has been a consistent quest for higher education (especially university) in Nigeria, due to epileptic academic system. Coupled with the total number of candidates seeking admission into the various higher institutions in Nigeria yearly. On the basis of this, it has become obvious that the existing higher institutions, which were mainly government- owned, cannot cope with the ever- increasing demand for higher education in Nigeria. One of the basic panaceas to this challenge is the liberalization of participation in the education sector. The study applied both historical and sociological methodology in its investigation. This study examined the history of higher education in Nigeria, from 1989 to 2012. In addition, it also examined the role played by the private sector in the Nigerian educational sector in this present dispensation. The writers recommended that there should be a consistent upsurge of private higher institutions in Nigeria to adequately address the challenge posed by high prospective students’ demand for university education. This is due to the fact that the government alone cannot handle the ever- increasing demand for higher education in Nigeria. Key words: Higher Education, Participation, Private Sector, Sustainable Development

Exchange Rate Volatility and International Trade In Nigeria

Volatile exchange rate makes international trade and investment decisions more difficult because volatility increases exchange rate risk. This study seeks to evaluate the impact of exchange rate volatility on international trade in Nigeria on the basis of annual data from 1980 to 2013, which was obtained from World Bank Development Indicators (WDI). Exchange rate volatility, gross national product (GDP), investment, interest rate, import and export were used to capture the causal relationship between exchange rate volatility and international trade and also the long-run and short-run relationship between exchange rate volatility and international trade. A review of the literature reveals that exchange rate volatility has a negative impact on international trade. The empirical analysis began with testing for stationarity of the variables by applying the Augmented Dickey-Fuller (ADF), this was followed by co-integration test, then the granger causality and the Error Correction Model (ECM). The co-integration test indicated that the variables are co-integrated which implies that a long-run relationship exist between the variables while the granger causality test showed that a causal relationship exist between international trade and exchange rate volatility. It was observed form the ECM analysis that exchange rate volatility negatively affects international trade. The study therefore recommend that the government should put in place exchange rate and trade policies that will promote greater exchange rate stability and trade conditions that will promote domestic production in the economy. In other to achieve this, the government should provide efficient infrastructural services like energy resources

Monetary Policy and Commercial Banks’ Performance in Nigeria

The study was carried out to examine the impact of monetary policy on commercial banks’ performance in Nigeria in a micro-panel analysis. Interest rate and money supply were used as proxies for monetary policy, while profit before tax (PBT) was used to represent commercial banks’ performance. Pooled regression, Fixed effect regression, and random effect regression were all carried out in the analysis. However, Hausman test revealed that fixed effect regression is the most appropriate. The results show that there is a positive relationship between banks’ profits and monetary policies as proxied by money supply and interest rate. However, interest rate was not statistically significant at 1% and 5% levels. This study therefore recommends that interest rate policy should be looked into by the monetary authority in a way that is friendly to loan advancement in the country. Key words: Monetary Policy, Fixed effect, Hausman test, Banks’ Profits, Nigeri