pH-Induced conformational isomerization of leghemoglobin from Arachis hypogea.

The pH dependence of proteins is related to the thermodynamic stability and electrostatic interactions in the native state of a protein. Here we report the pH-induced conformational transition of the heme protein leghemoglobin (Lb) isolated from root nodules of the leguminous plant Arachis hypogea. Unlike the other heme proteins myoglobin, hemoglobin, and cytochrome c, the structural characteristics and interactions of Lb is almost unknown, though its functional importance is already established since it binds oxygen to maintain the environment for N2 fixation. We investigated pH-induced unfolding of this protein and identified a number of conformational isomers using multiple fluorescence observables as a function of pH titration. We have characterized the acid- and base-induced conformational transitions among the structural states over the pH range 2-11. Depending on the solution conditions, Lb can exist in one of three phases: pH 2, 3, 4; pH 5, 6, 7; pH 8, 9, 10. The secondary structure as revealed by CD spectroscopy indicated the maximum percentage of α-helix to be present at pH 7, where the structure of Lb is also most rigid according to fluorescence anisotropy experiments. The fluorescence lifetime of tryptophan was observed to be maximum at pH 10 and minimum at pH 6, suggesting unfolding transitions of Lb. Thus, alteration of the microenvironment of the globin moiety during pH transition ultimately leads to the conformational change of this monomeric protein Lb.

Effect of ethnicity on the hypnotic and cardiovascular characteristics of propofol induction.

We compared the propofol dose causing loss of verbal response and suppression of bispectral index to 50, between 50 white and 50 black patients, aged 18-65 years. Propofol was administered at 40 mg.kg⁻¹.h⁻¹ and reduced to 8 mg.kg⁻¹.h⁻¹ when bispectral index fell to 50. We recorded heart rate and mean arterial pressure for 15 min in total and calculated, for this period, maximal percentage change from baseline for each. A statistician, blinded to patient ethnicity, found mean (SD) propofol dose for loss of verbal response in white and black patients to be 1.41 (0.37) mg.kg⁻¹ and 1.16 (0.25) mg.kg⁻¹, respectively (p < 0.001). Corresponding figures for maximal percentage change in heart rate were 14.1 (12.6) % and 7.5 (14.0) % (p = 0.015). Other differences were non-significant. The dose of propofol required for loss of verbal response, but not for suppression of bispectral index to 50, is lower in black than in white patients.

Assessment of burden in caregivers of Alzheimer's disease from India.

INTRODUCTION: Most of existing literature on dementia caregiving comes from Western countries but the caregiving experience appears to vary in different societies. The cultural norms and socioeconomic resources of India are in stark contrast to western societies, however the dementia caregiver burden remains understudied in Indian context. AIM: We aim to assess the burden in relation to key variables and explore its predictors in caregivers of Alzheimer's disease. METHOD: Thirty-two patient-caregiver dyads were selected. The dementia characteristics were assessed with Hindi Mental State Examination and Clinical Dementia Rating; burden was evaluated using Burden Assessment Schedule. RESULTS: The caregiver sample had an overall moderate degree of burden. The burden in patient's behavior and external support area increased with the degree of cognitive impairment. Caregivers for male patients were found to have a higher burden. The female caregivers perceived higher burden in physical and mental health, spouse related and caregiver's routine. The burden in caregivers from joint families did not differ from nuclear families except for a lower burden in external support area. On stepwise multiple regression, spousal relation, HMSE score and male patient emerged as significant predictors of total burden. CONCLUSION: There is a need to devote more research attention towards dementia caregivers from developing countries and to understand the culture-specific impact of caregiving.