Thermal unfolding monitored by spectroscopy or calorimetry is widely used to determine protein stability. Equilibrium thermodynamic analysis of such unfolding is often hampered by its irreversibility, which usually results from aggregation of thermally denatured protein. In addition, heatinduced protein misfolding and aggregation often lead to formation of amyloid-like structures. We propose a convenient method to monitor in real time protein aggregation during thermal folding/ unfolding transition by recording turbidity or 908 light scattering data in circular dichroism (CD) spectroscopic experiments. Since the measurements of turbidity and 908 light scattering can be done simultaneously with far-or near-UV CD data collection, they require no additional time or sample and can be directly correlated with the protein conformational changes monitored by CD. The results can provide useful insights into the origins of irreversible conformational changes and test the linkage between protein unfolding or misfolding and aggregation in various macromolecular systems, including globular proteins and protein-lipid complexes described in this study, as well as a wide range of amyloid-forming proteins and peptides.Keywords: circular dichroism spectroscopy; irreversible protein unfolding; turbidity; light scattering; asparaginase-2; high-density lipoprotein; amyloid; protein structure/folding; conformational changes; stability and mutagenesis; enzymes; thermodynamics; hydrodynamics; aggregation Thermal or chemical unfolding is generally used to determine thermodynamic protein stability, which is the Gibbs free energy difference between the folded and the unfolded states, DG = G U -G F . In thermal unfolding experiments, protein solution is heated at a constant rate, and changes in the protein conformation or their heat effects are monitored by spectroscopy or differential scanning calorimetry (DSC), respectively. The results, including the melting temperature (T m ), enthalpy (DH(T m )), and heat capacity increment (DC p ) of the unfolding, are used to determine protein stability function (DG(T)) (Privalov 1979;Pace et al. 1989). The key assumption behind this approach is that the protein unfolding is a thermodynamically reversible (that is, an equilibrium) transition. Although this assumption is usually valid for chemical denaturation, thermal denaturation (which is particularly widely used in protein stability studies) is often irreversible. The general root 3 These authors contributed equally to this work.

Background:The primary cicatricial alopecias (PCAs) are a rare group of diseases where hair follicle is the primary target of destruction. There are a few studies on histopathological and trichoscopic features of PCA.Aims:To study the clinical, trichoscopic, and histopathological characteristics of PCAs of the scalp and to find out the concordance between trichoscopic and histopathological diagnosis.Materials and Methods:We retrospectively analyzed the clinical, trichoscopic, and histopathological features of 24 PCA patients. Fisher's Chi-square exact test was done to find the significant trichoscopic and histopathological features. Cohen's kappa coefficient was used to determine the agreement between histopathological and trichoscopic diagnosis.Results:A total of 24 patients of PCA were seen with a male: female ratio of 2:1. There were 10 (41.7%) patients of discoid lupus erythematosus (DLE), 5 (20.8%) of lichen planopilaris (LPP), 3 (12.5%) of dissecting cellulitis of scalp, and 2 (8.3%) each of pseudopelade of brocq, folliculitis decalvans, and frontal fibrosing alopecia. The important histopathological findings of DLE were follicular plugging, vacuolar changes in the basal layer, necrotic keratinocytes, and superficial and deep perifollicular and perivascular lymphocytic infiltrate. Histopathology of LPP showed vacuolar changes in the basal layer and lichenoid infiltrate involving the infundibulum and isthmus. Trichoscopy of DLE showed follicular plugging, yellow dots, and thick arborizing blood vessels. The peripilar cast was important finding in LPP. The characteristic yellow dot with three-dimensional structure was noted in dissecting cellulitis of the scalp. The Cohen's kappa agreement was 0.89 between histopathological and trichoscopic diagnosis.Conclusion:The diagnosis of PCA is challenging because of overlapping features clinically and histopathologically. Trichoscopy may provide quick and reliable diagnosis and obviate the necessity of scalp biopsy in busy clinics.

Background:Cutaneous tuberculosis forms a small subset of extra pulmonary tuberculosis and has a worldwide distribution.Aims:The present study is an attempt to find out the incidence, clinical spectrum, and histopathological features of cutaneous tuberculosis.Materials and Methods:A total of 42 cases of newly diagnosed patients of cutaneous tuberculosis attending dermatology out patient department over a period of 1 year were included in the study. A detailed clinical examination and investigations including histopathological examination were carried out.Results:Scrofuloderma was the most common form seen in 50% cases followed by lupus vulgaris in 42.86%, tuberculosis verrucosa cutis in 4.76%, and lichen scrofulosorum in 2.38% cases. The Mantoux test was positive in 83.33% cases. Characteristic tuberculoid granulomas were seen in 72.22% cases of lupus vulgaris, 42.86% cases of scrofuloderma and all cases of tuberculosis verrucosa cutis and lichen scrofulosorum.Conclusion:Cutaneous tuberculosis is still highly prevalent in upper Assam. Early diagnosis and treatment are essential to prevent its complications.

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