Ganglioside GM1 Drives Hemin and Protoporphyrin Adsorption in Phospholipid Membranes: A Structural Study

Monosialoganglioside (GM1), a ubiquitous component of lipid rafts, and hemin, an integral part of heme proteins such as hemoglobin, are essential to the cell membranes of brain neurons and erythrocyte red blood cells for regulating cellular communication and oxygen transport. Protoporphyrin IX (PPIX) and its derivative hemin, on the contrary, show significant cytotoxic effects when in excess causing hematological diseases, such as thalassemia, anemia, malaria, and neurodegeneration. However, the in-depth molecular etiology of their interactions with the cell membrane has so far been poorly understood. Herein, the structure of the polymer cushion-supported lipid bilayer (SLB) of the binary mixture of phospholipid and GM1 in the presence of PPIX and its derivative hemin has been investigated to predict the molecular interactions in model phospholipid membranes. A high-resolution synchrotron-based X-ray scattering technique has been employed to explore the out-of-plane structure of the assembly at different compositions and concentrations. The structural changes have been complemented with the isobaric changes in the mean molecular area obtained from the Langmuir monolayer isotherm to predict the additive-induced membrane condensation and fluidization. PPIX-induced fluidization of phospholipid SLB without GM1 was witnessed, which was reversed to condensation with 2-fold higher structural changes in the presence of GM1. A hemin concentration-dependent linear condensing effect was observed in the pristine SLB. The effect was significantly reduced, and the linearity was observed to be lost in the mixed SLB containing GM1. Our study shows that GM1 alters the interaction of hemin and PPIX with the membrane, which could be explained with the aid of hydrophobic and electrostatic interactions. Our study indicates favorable and unfavorable interactions of GM1 with PPIX and hemin, respectively, in the membrane. The observed structural changes in both SLB and the underlying polymer cushion layer lead to the proposal of a molecule-specific interaction model that can benefit the pharmaceutical industries specialized for drug designing. Our study potentially enriches our fundamental biophysical understanding of neurodegenerative diseases and drug-membrane interactions.

Structural Flexibility of Proteins Dramatically Alters Membrane Stability─A Novel Aspect of Lipid-Protein Interaction

Protein isoforms are structural variants with changes in the overall flexibility predominantly at the tertiary level. For membrane associated proteins, such structural flexibility or rigidity affects membrane stability by playing modulatory roles in lipid-protein interaction. Herein, we investigate the protein chain flexibility mediated changes in the mechanistic behavior of phospholipid model membranes in the presence of two well-known isoforms, erythroid (ER) and nonerythroid (NER) spectrin. We show dramatic alterations of membrane elasticity and stability induced by spectrin in the Langmuir monolayers of phosphatidylocholine (PC) and phosphatidylethanolamine (PE) by a combination of isobaric relaxation, surface pressure-area isotherm, X-ray scattering, and microscopy measurements. The NER spectrin drives all monolayers to possess an approximately equal stability, and that required 25-fold increase and 5-fold decrease of stability in PC and PE monolayers, respectively. The untilting transition of the PC membrane in the presence of NER spectrin observed in X-ray measurements can explain better membrane packing and stability.

Spectrin: an alternate target for cytoskeletal drugs

Cytoskeletal drugs having enormous therapeutic potential act on the cytoskeletal components like actin, tubulin either by promoting polymerization or destabilizing the same. Here we present the interaction of the popular cytoskeletal drugs such as taxol, latrunculin and cytochalasin with spectrin, a huge protein with multi domains that forms the cytoskeletal network. Particularly, the actin binding domain of spectrin regulates the dynamics of the actin cytoskeleton. We followed the binding of these drugs to its actin binding domain and intact spectrin as well. These drugs bind with moderate affinity (K_b ∼ 10⁴ M^-1) and the interaction with actin binding domain is entropy driven and hydrophobic in nature as determined by Van't Hoff plot. The docking studies and molecular dynamics simulations further corroborate the experimental findings. Particularly the higher binding constants in the case of latrunculin and cytochalasin to the actin binding domain of spectrin suggest the binding sites are presumably located in its actin binding domain.Communicated by Ramaswamy H. Sarma.

Comparative Analysis of Tryptophan Dynamics in Spectrin and Its Constituent Domains: Insights from Fluorescence

Spectrin is a cytoskeletal protein ubiquitous in metazoan cells that acts as a liaison between the plasma membrane and the cellular interior and imparts mechanical stability to the plasma membrane. Spectrin is known to be highly dynamic, with an appreciable degree of torsional and segmental mobility. In this context, we have earlier utilized the red edge excitation shift (REES) approach to report the retention of restricted solvation dynamics and local structure in the vicinity of spectrin tryptophans on urea denaturation and loss of spectrin secondary structure. As a natural progression of our earlier work, in this work, we carried out a biophysical dissection of tryptophan solvation and rotational dynamics in spectrin and its constituent domains, in order to trace the origin of local structure retention observed in denatured spectrin. Our results show that the ankyrin binding domain (and, to a lesser extent, the β-tetramerization domain) is capable of retention of local structure, similar to that observed for intact spectrin. However, all α-chain domains studied exhibit negligible retention of local structure on urea denaturation. Such a stark chain-specific retention of local structure could originate from the fact that the β-chain domains possess specialized functions, where conservation of local (structural) integrity may be a prerequisite for optimum cellular function. To the best of our knowledge, these observations represent one of the first systematic biophysical dissections of spectrin dynamics in terms of its constituent domains and add to emerging literature on comprehensive domain-based analysis of spectrin organization, dynamics, and function.

Thermodynamics of adsorption of alcohol dehydrogenase on the gold nanoparticle surface: a model based analysis versus direct measurement

Characterization of the nanoparticle protein corona has gained tremendous importance lately. The parameters which quantitatively establish a specific nanoparticle-protein interaction need to be measured accurately since good quality data are necessary for the elucidation of the underlying mechanism and accurate molecular dynamics simulation. Here, we have employed surface sensitive second harmonic light scattering (SHLS) for investigating the adsorption of a tetrameric protein, alcohol dehydrogenase (ADH, Saccharomyces cerevisiae 147 kDa), on 16 nm, 27 nm, 41 nm, and 69 nm citrate capped gold nanoparticles (GNPs) in aqueous phosphate buffer at pH 7. We have extracted the binding constant, number of ADH bound per GNP, Gibbs free energy (ΔG°) from the decay of the second harmonic scattered signal as a function of protein concentration using a modified version of the Langmuir adsorption isotherm. The data obtained were checked with another technique, dynamic light scattering, using the same modified Langmuir model (MLM). While the binding constants measured by the two methods are in agreement, the number of ADH bound to each GNP obtained by the two methods varies a lot. In order to further probe this binding independent of a model fitting, we used an orthogonal fluorescence assay which measures the number of ADH bound to a GNP directly, and no model-fitting is necessary. We then used temperature dependent SHLS to measure the heat of adsorption (ΔH°) and entropy (ΔS°) for ADH-GNP corona formation. We found that the equilibrium binding constant (K_b) obtained from SHLS is of the order of 10⁹ M^-1 and the formation of the GNP-ADH corona is spontaneous with ΔG° ∼ -55 kJ mol^-1. However, the adsorption is modestly endothermic, accompanied by a large increase in entropy. Stated differently, GNP-ADH corona formation is entropically driven. This is perhaps due to the tremendous disruption of the water structure at the negatively charged interface upon the arrival of the protein within the bonding distance to it. We believe that the SHLS technique is highly sensitive and reliable, at very low concentrations of both nanoparticles and proteins, for the quantitative estimation of the thermodynamic parameters of nanoparticle-protein corona formation, where many other techniques may fall short.

Adverse childhood experiences and substance misuse in young people in India: results from the multisite cVEDA cohort

BACKGROUND

Adverse childhood experiences (ACEs) increases vulnerability to externalising disorders such as substance misuse. The study aims to determine the prevalence of ACEs and its association with substance misuse.

METHODS

Data from the Consortium on Vulnerability to Externalising Disorders and Addictions (cVEDA) in India was used (n = 9010). ACEs were evaluated using the World Health Organisation (WHO) Adverse Childhood Experiences International Questionnaire whilst substance misuse was assessed using the WHO Alcohol, Smoking and Substance Involvement Screening Test. A random-effects, two-stage individual patient data meta-analysis explained the associations between ACEs and substance misuse with adjustments for confounders such as sex and family structure.

RESULTS

1 in 2 participants reported child maltreatment ACEs and family level ACEs. Except for sexual abuse, males report more of every individual childhood adversity and are more likely to report misusing substances compared with females (87.3% vs. 12.7%). In adolescents, family level ACEs (adj OR 4.2, 95% CI 1.5-11.7) and collective level ACEs (adj OR 6.6, 95% CI 1.4-31.1) show associations with substance misuse whilst in young adults, child level ACEs such as maltreatment show similar strong associations (adj OR 2.0, 95% CI 1.1-3.5).

CONCLUSION

ACEs such as abuse and domestic violence are strongly associated with substance misuse, most commonly tobacco, in adolescent and young adult males in India. The results suggest enhancing current ACE resilience programmes and 'trauma-informed' approaches to tackling longer-term impact of ACEs in India.

FUNDING

Newton Bhabha Grant jointly funded by the Medical Research Council, UK (MR/N000390/1) and the Indian Council of Medical Research (ICMR/MRC-UK/3/M/2015-NCD-I).

Effects of free soluble iron on thermal aggregation of hemoglobin

Aggregation of hemoglobin is implicated in the presentation of diseases like sickle cell disease and thalassemia. Hallmark of the disease being imbalance in the production of globin chains leading to aggregation of excess globin chains and aberrant hemoglobins associated with the disease, broadly categorized as hemoglobinopathy. We have studied thermal aggregation of hemoglobin at 70 °C and pH 6.5 using light scattering, flow cytometry and optical microscopy and tried to investigate effects of few abundant soluble metal ions on such aggregation. Our study indicate that only iron, both in Fe²⁺ and Fe³⁺ forms, could inhibit hemoglobin aggregation and the extent of inhibition was 60% in presence of 100 mgL^-1 FeCl₃. Similar effect was not seen in lysozyme aggregation. Metal ions such as, Cu²⁺, Zn²⁺ and Ni²⁺ also did not have any significant effects on hemoglobin aggregation. Results show this important chaperone like behavior of free iron affecting the kinetics and yield of the aggregation process which could have important consequence in the extent of severity of such hematological diseases.

Multiple Functions of Spectrin: Convergent Effects

Spectrin is a multifunctional, multi-domain protein most well known in the membrane skeleton of mature human erythrocytes. Here we review the literature on the crosstalk of the chaperone activity of spectrin with its other functionalities. We hypothesize that the chaperone activity is derived from the surface exposed hydrophobic patches present in individual "spectrin-repeat" domains and show a competition between the membrane phospholipid binding functionality and chaperone activity of spectrin. Moreover, we show that post-translational modifications such as glycation which shield these surface exposed hydrophobic patches, reduce the chaperone function. On the other hand, oligomerization which is linked to increase of hydrophobicity is seen to increase it. We note that spectrin seems to prefer haemoglobin as its chaperone client, binding with it preferentially over other denatured proteins. Spectrin is also known to interact with unstable haemoglobin variants with a higher affinity than in the case of normal haemoglobin. We propose that chaperone activity of spectrin could be important in the cellular biochemistry of haemoglobin, particularly in the context of diseases.

A multicentre observational study on the epidemiology, risk factors, management and outcomes of mucormycosis in India

OBJECTIVES

To describe the epidemiology, management and outcome of individuals with mucormycosis; and to evaluate the risk factors associated with mortality.

METHODS

We conducted a prospective observational study involving consecutive individuals with proven mucormycosis across 12 centres from India. The demographic profile, microbiology, predisposing factors, management and 90-day mortality were recorded; risk factors for mortality were analysed.

RESULTS

We included 465 patients. Rhino-orbital mucormycosis was the most common (315/465, 67.7%) presentation followed by pulmonary (62/465, 13.3%), cutaneous (49/465, 10.5%), and others. The predisposing factors included diabetes mellitus (342/465, 73.5%), malignancy (42/465, 9.0%), transplant (36/465, 7.7%), and others. Rhizopus species (231/290, 79.7%) were the most common followed by Apophysomyces variabilis (23/290, 7.9%), and several rare Mucorales. Surgical treatment was performed in 62.2% (289/465) of the participants. Amphotericin B was the primary therapy in 81.9% (381/465), and posaconazole was used as combination therapy in 53 (11.4%) individuals. Antifungal therapy was inappropriate in 7.6% (30/394) of the individuals. The 90-day mortality rate was 52% (242/465). On multivariate analysis, disseminated and rhino-orbital (with cerebral extension) mucormycosis, shorter duration of symptoms, shorter duration of antifungal therapy, and treatment with amphotericin B deoxycholate (versus liposomal) were independent risk factors of mortality. A combined medical and surgical management was associated with a better survival.

CONCLUSIONS

Diabetes mellitus was the dominant predisposing factor in all forms of mucormycosis. Combined surgical and medical management was associated with better outcomes. Several gaps surfaced in the management of mucormycosis. The rarer Mucorales identified in the study warrant further evaluation.

1410Clinical predictors of NT-proBNP response to early initiation of sacubitril/valsartan after hospitalisation for decompensated heart failure: An analysis of the TRANSITION study

Background

NT-proBNP has diagnostic and prognostic value in patients with heart failure (HF). Compared with enalapril, sacubitril/valsartan (S/V) significantly reduced NT-proBNP within 1 week (wk) of administration and reduced HF re-hospitalisation in patients with acute decompensated HF (ADHF) in PIONEER-HF. Identification of predictors of NT-proBNP reduction with S/V could aid prognostication following hospitalisation.

Methods

TRANSITION (NCT02661217) is an open label study in stabilised ADHF patients with HFrEF that compared S/V initiation pre- versus post-discharge (within 2 wk of discharge). Baseline NT-proBNP was measured at randomisation in both S/V groups (n=950). Clinical predictors of favourable response of NT-proBNP to S/V therapy (defined as reduction to <1000 pg/ml or >30% reduction vs. baseline) were studied at discharge, 4 wk and 10 wk post-randomisation.

Results

Median NT-proBNP at randomisation was similar in patients with S/V started pre- and post-discharge (1919 vs 1659 pg/ml). In patients receiving S/V in-hospital, NT-proBNP was reduced by 28% at discharge, compared to a 3% reduction in patients receiving optimised standard of care (between group p<0.001). A favorable response was reached in 46% vs 18% patients at discharge, 46% vs 42% at 4 weeks and 51% vs 48% at 10 weeks in pre- vs post-discharge groups. (Figure 1). Predictors of favourable NT-proBNP response to S/V at discharge were hypertension and shorter time from admission to first S/V dose. At 4 wk after randomisation, NT-proBNP was reduced similarly in patients started on S/V pre- and post-discharge. When the two S/V initiation groups were combined, predictors of favorable NT-proBNP response at 4 wk were higher initial dose of S/V (≥49/51 mg b.i.d.), higher baseline levels of NT-proBNP, de novo HF hospitalisation, ACEI/ARB naïve, lower baseline creatinine, no atrial fibrillation (AFib), no prior myocardial infarction (MI). A further reduction in NT-proBNP was seen at 10 wk post-randomisation in patients started on S/V pre- and post-discharge (38% vs 34%, between group p=0.250). Predictors of favourable NT-proBNP response to S/V were similar at 4 wk and 10 wk post-randomisation.

Conclusion

In-hospital initiation of sacubitril/valsartan shortly after stabilisation was associated with a prompt improvement of NT-proBNP already at discharge, whereas higher baseline levels of NT-proBNP, higher starting dose, absence of AFib and MI history, de novo HF and ACEI/ARB naïve status were associated with favourable NT-proBNP response in the vulnerable phase after discharge.

Acknowledgement/Funding

The TRANSITION study was funded by Novartis

Chaperone potential of erythroid spectrin: Effects of hemoglobin interaction, macromolecular crowders, phosphorylation and glycation

Spectrin, the major protein component of the erythrocyte membrane skeleton has chaperone like activity and is known to bind membrane phospholipids and hemoglobin. We have probed the chaperone activity of spectrin in presence of hemoglobin and phospholipid SUVs of different compositions to elucidate the effect of phospholipid/hemoglobin binding on chaperone function. It is seen that spectrin displays a preference for hemoglobin over other substrates leading to a decrease in chaperone activity in presence of hemoglobin. A competition is seen to exist between phospholipid binding and chaperone function of spectrin, in a dose dependent manner with the greatest extent of decrease being seen in case of phospholipid vesicles containing aminophospholipids e.g. PS and PE which may have implications in diseases like hereditary spherocytosis where mutation in spectrin is implicated in its detachment from cell membrane. To gain a clearer understanding of the chaperone like activity of spectrin under in-vivo like conditions we have investigated the effect of macromolecular crowders as well as phosphorylation and glycation states on chaperone activity. It is seen that the presence of non-specific, protein and non-protein macromolecular crowders do not appreciably affect chaperone function. Phosphorylation also does not affect the chaperone function unlike glycation which progressively diminishes chaperone activity. We propose a model where chaperone clients adsorb onto spectrin's surface and processes that bind to and occlude these surfaces decrease chaperone activity.

Monitoring treatment response in chronic pulmonary aspergillosis: role of clinical, spirometric and immunological markers

OBJECTIVES

The treatment response in chronic pulmonary aspergillosis (CPA) is usually assessed based on the improvement in clinical and imaging findings. Herein, we evaluate serum Aspergillus fumigatus-specific IgG, serum galactomannan, weight change, and lung function for assessing treatment response in subjects with CPA.

METHODS

We categorized treatment response as favourable (improved or stable clinical response with radiologically improved or stable disease) or unfavourable (worsening of symptoms or radiological progression) after 6 months of treatment with antifungal azoles. We measured A. fumigatus-specific IgG, serum galactomannan, weight, and lung function at baseline, 3 months, and 6 months in those with favourable and unfavourable treatment response.

RESULTS

One hundred and twenty-six consecutive treatment-naïve subjects (53.2% (67/126) males; mean ± SD age, 42.3 ± 14.7 years) with CPA were included. One hundred and six and 20 were classified as having favourable and unfavourable response, respectively. After 6 months of treatment, the decline in serum A. fumigatus-specific IgG (n = 119) was similar in those with favourable or unfavourable response (mean ± SD, -26.3 ± 45.5 mgA/L vs. -3.4 ± 65.6 mgA/L; p 0.20). There was no significant change in the serum galactomannan (favourable vs. unfavourable: mean ± SD, -0.11 ± 2.8 vs. -0.62 ± 2; p 0.92) or FEV1 (favourable vs. unfavourable: mean ± SD, 24 ± 250 mL vs. -62 ± 154 mL; p 0.19) after 6 months of treatment. There was significant loss of weight (mean ± SD, -2.5 ± 4.5 kg) in subjects with unfavourable response.

CONCLUSION

Serum A. fumigatus-specific IgG and serum galactomannan inconsistently decrease following treatment and may not be useful indicators for monitoring treatment response in CPA. Similarly, there is little change in pulmonary function following treatment. A gain in body weight is seen in those with favourable response.

Epidemiology and clinical characteristics of invasive mould infections: A multicenter, retrospective analysis in five Asian countries

Formal, large-scale, multicenter studies of invasive mould infection (IMI) in Asia are rare. This 1-year, retrospective study was designed to assess the incidence and clinical determinants of IMI in centers in five countries (Thailand, Taiwan, Singapore, China, India). Patients treated in a single year (2012) were identified through discharge diagnoses, microbiology, and histopathology logs, and entered based on published definitions of IMI. A total of 155 cases were included (median age 54 years; 47.7% male). Of these, 47.7% had proven disease; the remainder had probable IMI. The most frequent host factors were prolonged steroid use (39.4%) and recent neutropenia (38.7%). Common underlying conditions included diabetes mellitus (DM; 30.9%), acute myeloid leukemia (19.4%), and rheumatologic conditions (11.6%). DM was more common in patients with no recent history of neutropenia or prolonged steroid use (P = .006). The lung was the most frequently involved site (78.7%), demonstrating a range of features on computed tomography (CT). Aspergillus was the most common mould cultured (71.6%), primarily A. fumigatus and A. flavus, although proportions varied in different centers. The most often used antifungal for empiric therapy was conventional amphotericin. Ninety-day mortality was 32.9%. This is the first multicenter Asian study of IMI not limited to specific patient groups or diagnostic methods. It suggests that DM and rheumatologic conditions be considered as risk factors for IMI and demonstrates that IMI should not be ruled out in patients whose chest features on CT do not fit the conventional criteria.

Structure-activity relationship of heme and its analogues in membrane damage and inhibition of fusion

Under pathological conditions, such as sickle cell disease and malaria, heme concentration increases considerably, and it induces membrane damage. As sickled and normal erythrocytes contain high cholesterol: phospholipid ratio, we investigated the role of lipid composition, chain length, and unsaturation on the partitioning and leakage of hemin in phospholipid vesicles. To establish structure-activity relationship in membrane damage, experiments with two other analogues, protoporphyrin-IX and hematoporphyrin (HP) were also carried out. Hemin and its analogues localize differently in membranes and exhibit distinct roles in partitioning, leakage and fusion. Hemin and HP trigger more leakage in the presence of aminophospholipids, whereas cholesterol buffers the destabilizing effect remarkably. Inhibition of fusion by hemin further suggests its unexplored and important role in membrane trafficking, particularly under diseased conditions.

Effects of GM1 on brain spectrin-aminophospholipid interactions

Spectrin, a major component of the membrane skeletal meshwork of metazoan cells, is implicated to associate with membrane domains and is known to act as a scaffold for stabilization and activation of different signalling modules. We have studied the effect of GM1 (monosialotetrahexosyl ganglioside), a well-known model ganglioside and a signalling moiety, on the interaction of non-erythroid brain spectrin with both saturated and unsaturated aminophospholipids by spectroscopic methods. We observe that GM1 modulates brain spectrin-aminophospholipid interaction to the greatest degree whereas its effect on erythroid spectrin is not as pronounced. Fluorescence quenching studies show that brain spectrin interacts with DMPC/DMPE-based vesicles with a 10-fold increased affinity in presence of very low amounts of 2% and 5% GM1, and the extent of quenching decreases progressively in presence of increasing amounts of GM1. Interaction of brain spectrin with unsaturated membrane systems of DOPC/DOPE weakens in presence GM1. Increase in the mean lifetime of the Trp residues of brain spectrin in presence of GM1 indicates change in the microenvironment of spectrin, without affecting the secondary structure of the protein significantly. Studies on pressure - area isotherm of Langmuir-Blodgett monolayer and Brewster's angle microscopy show that GM1 has an expanding effect on the aminophospholipid monolayers, and ordered regions in DMPC/DMPE mixed monolayers are formed and are stabilized at higher pressure. GM1-induced fluidization of the phospholipid membranes and probable physical contact between bulky sugar head group of GM1 and spectrin, may explain the modulatory role of GM1 on aminophospholipid interactions with nonerythroid brain spectrin.

Standardization of a two-step real-time polymerase chain reaction based method for species-specific detection of medically important Aspergillus species

PURPOSE

Standardization of Aspergillus polymerase chain reaction (PCR) poses two technical challenges (a) standardization of DNA extraction, (b) optimization of PCR against various medically important Aspergillus species. Many cases of aspergillosis go undiagnosed because of relative insensitivity of conventional diagnostic methods such as microscopy, culture or antigen detection. The present study is an attempt to standardize real-time PCR assay for rapid sensitive and specific detection of Aspergillus DNA in EDTA whole blood.

MATERIALS AND METHODS

Three nucleic acid extraction protocols were compared and a two-step real-time PCR assay was developed and validated following the recommendations of the European Aspergillus PCR Initiative in our setup. In the first PCR step (pan-Aspergillus PCR), the target was 28S rDNA gene, whereas in the second step, species specific PCR the targets were beta-tubulin (for Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus), gene and calmodulin gene (for Aspergillus niger).

RESULTS

Species specific identification of four medically important Aspergillus species, namely, A. fumigatus, A. flavus, A. niger and A. terreus were achieved by this PCR. Specificity of the PCR was tested against 34 different DNA source including bacteria, virus, yeast, other Aspergillus sp., other fungal species and for human DNA and had no false-positive reactions. The analytical sensitivity of the PCR was found to be 102 CFU/ml.

CONCLUSION

The present protocol of two-step real-time PCR assays for genus- and species-specific identification for commonly isolated species in whole blood for diagnosis of invasive Aspergillus infections offers a rapid, sensitive and specific assay option and requires clinical validation at multiple centers.

Identification of Malassezia species by MALDI-TOF MS after expansion of database

The taxonomy of Malassezia species is evolving with introduction of molecular techniques, and difficulty is faced to identify the species by phenotypic methods. Among 15 known Malassezia species, the present Bruker database could identify only 2 species. The present study was aimed to improve Matrix -assisted laser desorption ionization time-flight mass spectrometry (MALDI-TOF MS) based identification of Malassezia species. A total of 88 isolates (DNA sequencing confirmed) for database preparation and, for the validation of database, 190 isolates confirmed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) were used. The main spectrum profile dendrogram showed the sufficient discrimination between all the species by MALDI-TOF MS. The updated Malassezia database could identify 94.7% and 5.3% strains to the species and genus level, respectively. MALDI-TOF MS is a significantly reliable technique, and results were comparable with PCR-RFLP with kappa value 0.9. In conclusion, MALDI-TOF MS could be a possible alternative tool to other molecular methods for rapid and accurate identification of Malassezia species.

Diagnosis and management of Aspergillus diseases: executive summary of the 2017 ESCMID-ECMM-ERS guideline

The European Society for Clinical Microbiology and Infectious Diseases, the European Confederation of Medical Mycology and the European Respiratory Society Joint Clinical Guidelines focus on diagnosis and management of aspergillosis. Of the numerous recommendations, a few are summarized here. Chest computed tomography as well as bronchoscopy with bronchoalveolar lavage (BAL) in patients with suspicion of pulmonary invasive aspergillosis (IA) are strongly recommended. For diagnosis, direct microscopy, preferably using optical brighteners, histopathology and culture are strongly recommended. Serum and BAL galactomannan measures are recommended as markers for the diagnosis of IA. PCR should be considered in conjunction with other diagnostic tests. Pathogen identification to species complex level is strongly recommended for all clinically relevant Aspergillus isolates; antifungal susceptibility testing should be performed in patients with invasive disease in regions with resistance found in contemporary surveillance programmes. Isavuconazole and voriconazole are the preferred agents for first-line treatment of pulmonary IA, whereas liposomal amphotericin B is moderately supported. Combinations of antifungals as primary treatment options are not recommended. Therapeutic drug monitoring is strongly recommended for patients receiving posaconazole suspension or any form of voriconazole for IA treatment, and in refractory disease, where a personalized approach considering reversal of predisposing factors, switching drug class and surgical intervention is also strongly recommended. Primary prophylaxis with posaconazole is strongly recommended in patients with acute myelogenous leukaemia or myelodysplastic syndrome receiving induction chemotherapy. Secondary prophylaxis is strongly recommended in high-risk patients. We strongly recommend treatment duration based on clinical improvement, degree of immunosuppression and response on imaging.

Status of Membrane Asymmetry in Erythrocytes: Role of Spectrin

Spectrin-based proteinaceous membrane skeletal network has been found to be implicated in membrane disorders like hereditary spherocytosis (HS). HS greatly affects eryptosis via loss of membrane asymmetry which is seen to be the case in haemoglobin disorders like thalassemia and sickle cell disease as well. The biological implications of the status of membrane asymmetry are strongly correlated to spectrin interactions with aminophospholipids, e.g. PE and PS. Fluorescence and X-ray reflectivity (XRR) measurements of spectrin interactions with small unilamellar vesicles (SUVs) and cushioned bilayers of phospholipids, respectively, were studied. Both the XRR and fluorescence measurements led to the characterization of spectrin orientation on the surface of lipid bilayer of phosphatidylcholine (PC) and PC/aminophospholipid mixed membrane systems showing formation of a uniform layer of spectrin on top of the mixed phospholipid bilayer. Fluorescence studies show that spectrin interacts with PC and phosphatidylethanolamine (PE)/phosphatidylserine (PS) membranes with binding dissociation constants (K_d) in the nanomolar range indicating the role of spectrin in the maintenance of the overall membrane asymmetry of erythrocytes.

Friction Stir Processing of Stainless Steel for Ascertaining Its Superlative Performance in Bioimplant Applications

Substrate-cell interactions for a bioimplant are driven by substrate's surface characteristics. In addition, the performance of an implant and resistance to degradation are primarily governed by its surface properties. A bioimplant typically degrades by wear and corrosion in the physiological environment, resulting in metallosis. Surface engineering strategies for limiting degradation of implants and enhancing their performance may reduce or eliminate the need for implant removal surgeries and the associated cost. In the current study, we tailored the surface properties of stainless steel using submerged friction stir processing (FSP), a severe plastic deformation technique. FSP resulted in significant microstructural refinement from 22 μm grain size for the as-received alloy to 0.8 μm grain size for the processed sample with increase in hardness by nearly 1.5 times. The wear and corrosion behavior of the processed alloy was evaluated in simulated body fluid. The processed sample demonstrated remarkable improvement in both wear and corrosion resistance, which is explained by surface strengthening and formation of a highly stable passive layer. The methylthiazol tetrazolium assay demonstrated that the processed sample is better in supporting cell attachment, proliferation with minimal toxicity, and hemolysis. The athrombogenic characteristic of the as-received and processed samples was evaluated by fibrinogen adsorption and platelet adhesion via the enzyme-linked immunosorbent assay and lactate dehydrogenase assay, respectively. The processed sample showed less platelet and fibrinogen adhesion compared with the as-received alloy, signifying its high thromboresistance. The current study suggests friction stir processing to be a versatile toolbox for enhancing the performance and reliability of currently used bioimplant materials.

Controlling a possible outbreak of Candida auris infection: lessons learnt from multiple interventions

BACKGROUND

Multidrug-resistant Candida auris infection has been reported from five continents in recent years. The prevalence of C. auris invasive infection has been estimated at 5.3% for intensive-care-acquired candidaemia in India. The transmission of the organism between the patients and from environment to patients is rapid.

AIM

To understand the intra-hospital dynamics of C. auris transmission and to determine the possible interventions to prevent its spread.

METHODS

Surveillance of intensive care units was carried out to assess patient colonization, environmental contamination and hand carriage of the yeast among healthcare workers. Interventions including chlorhexidine washing of patients and decontamination of environmental surfaces with stabilized hydrogen peroxide disinfectant (Ecoshield) were undertaken. We further evaluated the effectiveness of frequently used disinfectants in the hospital against C. auris on various inanimate surfaces, and its persistence on hospital fabrics.

FINDINGS

Three cases of C. auris bloodstream infection were detected over a period of three months. Many patients admitted at the same time, in the same area, were colonized by C. auris. Surveillance detected C. auris contamination of environmental surfaces and hands of healthcare workers. Interventions such as chlorhexidine washing and appropriate use of disinfectants could eradicate C. auris from patients and hospital environment.

CONCLUSION

The frequently used disinfectants in our hospital and current hand hygiene practices were efficient against C. auris if proper contact time and procedures were followed. Evaluation of possible persistence of C. auris on dry fabrics showed that they can persist for up to seven days.

Protein-Protein Interaction Probed by Label-free Second Harmonic Light Scattering: Hemoglobin Adsorption on Spectrin Surface as a Case Study

In this article, we have studied the binding of different naturally occurring hemoglobin (Hb) variants on erythrocyte skeletal protein, spectrin surface using the label free nondestructive second harmonic light scattering (SHLS) technique in aqueous buffer. Hemoglobin variants like sickle hemoglobin (HbS) and hemoglobin E (HbE) were chosen as they associate with sickle cell disease and HbEβ-thalassemia, respectively, and their interaction with spectrin is compared with normal adult hemoglobin (HbA). The concentration dependent change in the second harmonic light intensity from nanomolar spectrin solution has been measured after addition of small aliquots of hemoglobins. From the second harmonic titration data, the binding constant is calculated using a modified Langmuir adsorption model of hemoglobin binding to the spectrin surface. Interestingly, it is found that the binding constant for HbE (13.8 × 10⁸ M^-1) is 1 order of magnitude higher than that of HbS (1.6 × 10⁸ M^-1) or HbA (2.1 × 10⁸ M^-1) which indicates higher affinity of HbE for spectrin compared to HbA and HbS. The number of the Hb molecules bound to the spectrin surface was estimated to be of the order of hundred's which is determined for the first time.

Flow Cytometric Analysis of Protein Aggregates

BACKGROUND

Misfolding of proteins often leads to aggregation. Accumulation of diverse protein aggregates in various cells, tissue and organs is the hallmark of many diseases, such as Alzheimer's disease and Parkinson's disease.

OBJECTIVES

The main objective of this study was to present a novel method of characterization of protein aggregates, associated with differential toxicity with different size and composition in vitro using flow cytometry.

METHODS

A Beckman Coulter Epics XL flow cytometer with argon ion laser operating at 488 nm was used for flow cytometry analysis. The voltage and the gain settings for individual channels were set at high voltage and gain for the detections of autofluorescence, fluorescence of adsorbed Congo red, forward scattering (FSC) and side scattering (SSC) intensities from the aggregates of proteins and nanoparticles. Each sample was analyzed to characterize and quantify the number of aggregates with a limit of maximum 20,000 events. The flow cytometry data were analyzed using Flowing software version 2.5.1 and Origin 8.0.

RESULTS

Autofluorescence and scattering intensities could distinguish between amyloid and nonamyloid aggregates. Dot plots of both side scattering (SSC) and forward scattering (FSC) intensities also showed characteristic fingerprint of both the types of aggregates when compared with those of well known nanoparticles of oxides of Fe and Cu.

CONCLUSION

This work reports a novel, simple and robust flow cytometric method of characterization of protein aggregates of different size and composition which would find wider application in characterization of biomolecular aggregates, in general.

Substrate specificity in the context of molecular chaperones

Molecular chaperones are one of the key players in protein biology and as such their structure and mechanism of action have been extensively studied. However the substrate specificity of molecular chaperones has not been well investigated. This review aims to summarize what is known about the substrate specificity and substrate recognition motifs of chaperones so as to better understand what substrate specificity means in the context of molecular chaperones. Available literature shows that the majority of chaperones have broad substrate range and recognize non-native conformations of proteins depending on recognition of hydrophobic and/or charged patches. Based on these recognition motifs chaperones can select for early, mid or late folding intermediates. Another major contributor to chaperone specificity are the co-chaperones they interact with as well as the sub-cellular location they are expressed in and the inducability of their expression. Some chaperones which have only one or a few known substrates are reported. In their case the mode of recognition seems to be specific structural complementarity between chaperone and substrate. It can be concluded that the vast majority of chaperones do not show a high degree of specificity but recognize elements that signal non-native protein conformation and their substrate range is modulated by the context they function in. However a few chaperones are known that display exquisite specificity of their substrate e.g. mammalian heat shock protein 47 collagen interaction. © 2017 IUBMB Life, 69(9):647-659, 2017.

Kinetic percolation

We demonstrate that kinetic aggregation forms superaggregates that have structures identical to static percolation aggregates, and these superaggregates appear as a separate phase in the size distribution. Diffusion limited cluster-cluster aggregation (DLCA) simulations were performed to yield fractal aggregates with a fractal dimension of 1.8 and superaggregates with a fractal dimension of D=2.5 composed of these DLCA supermonomers. When properly normalized to account for the DLCA fractal nature of their supermonomers, these superaggregates have the exact same monomer packing fraction, scaling law prefactor, and scaling law exponent (the fractal dimension) as percolation aggregates; these are necessary and sufficient conditions for same structure. The size distribution remains monomodal until these superaggregates form to alter the distribution. Thus the static percolation and the kinetic descriptions of gelation are now unified.

A prospective international Aspergillus terreus survey: an EFISG, ISHAM and ECMM joint study

OBJECTIVES

A prospective international multicentre surveillance study was conducted to investigate the prevalence and amphotericin B susceptibility of Aspergillus terreus species complex infections.

METHODS

A total of 370 cases from 21 countries were evaluated.

RESULTS

The overall prevalence of A. terreus species complex among the investigated patients with mould-positive cultures was 5.2% (370/7116). Amphotericin B MICs ranged from 0.125 to 32 mg/L, (median 8 mg/L).

CONCLUSIONS

Aspergillus terreus species complex infections cause a wide spectrum of aspergillosis and the majority of cryptic species display high amphotericin B MICs.

Effect of pH on stability, conformation, and chaperone activity of erythroid & non-erythroid spectrin

Spectrin, a major component of the eukaryotic membrane skeleton, has been shown to have chaperone like activity. Here we investigate the pH induced changes in the structure and stability of erythroid and brain spectrin by spectroscopic methods. We also correlate these changes with modulations of chaperone potential at different pH. We have followed the pH induced structural changes by circular dichroism spectroscopy and intrinsic tryptophan fluorescence. It is seen that lowering the pH from 9 has little effect on structure of the proteins till about pH6. At pH4, there is significant change of the secondary structure of the proteins, along with a 5nm hypsochromic shift of the emission maxima. Below pH4 the proteins undergo acid denaturation. Probing exposed hydrophobic patches on the proteins using protein-bound 8-anilinonaphthalene-1-sulfonate fluorescence demonstrates that there is higher solvent accessibility of hydrophobic surfaces in both forms of spectrin at around pH4. Dynamic light scattering and 90° light scattering studies show that the both forms of spectrin forms oligomers at pH~4. Chemical unfolding data shows that these oligomers are less stable than the tetrameric form. Aggregation studies with BSA show that at pH4, both spectrins exhibit better chaperone activity. This enhancement of chaperone like activity appears to result from an increase in regions of solvent-exposed hydrophobicity and oligomeric state of the spectrins which in turn are induced by moderately acid pH. This may have in-vivo implications in cells facing stress conditions where cytoplasmic pH is lowered.

High fungal spore burden with predominance of Aspergillus in hospital air of a tertiary care hospital in Chandigarh

The prevalence of fungal spores in the hospital air is essential to understand the hospital-acquired fungal infections. Air conditioners (ACs) used in hospitals may either reduce spores in air or be colonised by fungi and aid in its dissemination. The present study was conducted to assess the fungal spore burden in AC and non-AC areas. We found a high fungal spore count in air irrespective of whether the area was AC or non-AC. The most predominant species isolated were Aspergillus flavus and Aspergillus fumigatus. Such high concentrations of pathogenic fungi in air may predispose individuals to develop disease.

A Study of Microalbuminuria (MAU) and Advanced Glycation End Products (AGEs) Levels in Diabetic and Hypertensive Subjects

The prevalence of non-communicable diseases like diabetes mellitus (DM) and hypertension (HTN) is growing worldwide. Both lead to nephropathy if not controlled effectively. Microalbuminuria (MAU) is recognized as an early predictor for nephropathy. Additionally, the timely detection of advanced glycation end products (AGEs) is also considered to be an important prognostic factor for diabetic nephropathies. Hence, screening for the early detection of MAU and AGEs would be an useful and relatively inexpensive laboratory test for early clinical diagnosis for the incidence of nephropathy in these diseases. This study was conducted in DM, HTN and pregnancy induced hypertensive (PIH) subjects. MAU and N^ε-Carboxymethyllysine (CML) levels were estimated by in-house RIA kits in the patient groups and controls, while the total AGEs level in serum was determined by ELISA. The levels of MAU, CML and AGE-BSA were observed to be significantly higher in DM, HTN and PIH subjects compared to controls (p < 0.001). Increased serum CML and AGEs levels in DM, HTN and PIH subjects indicated ongoing glycemic damage and their susceptibility to develop renal complications.

A Possible Role of the Full-Length Nascent Protein in Post-Translational Ribosome Recycling

Each cycle of translation initiation in bacterial cell requires free 50S and 30S ribosomal subunits originating from the post-translational dissociation of 70S ribosome from the previous cycle. Literature shows stable dissociation of 70S from model post-termination complexes by the concerted action of Ribosome Recycling Factor (RRF) and Elongation Factor G (EF-G) that interact with the rRNA bridge B2a/B2b joining 50S to 30S. In such experimental models, the role of full-length nascent protein was never considered seriously. We observed relatively slow release of full-length nascent protein from 50Sof post translation ribosome, and in that process, its toe prints on the rRNA in vivo and in in vitro translation with E.coli S30 extract. We reported earlier that a number of chemically unfolded proteins like bovine carbonic anhydrase (BCA), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), lysozyme, ovalbumin etc., when added to free 70Sin lieu of the full length nascent proteins, also interact with identical RNA regions of the 23S rRNA. Interestingly the rRNA nucleotides that slow down release of the C-terminus of full-length unfolded protein were found in close proximity to the B2a/B2b bridge. It indicated a potentially important chemical reaction conserved throughout the evolution. Here we set out to probe that conserved role of unfolded protein conformation in splitting the free or post-termination 70S. How both the RRF-EFG dependent and the plausible nascent protein–EFG dependent ribosome recycling pathways might be relevant in bacteria is discussed here.

Photochromic histone deacetylase inhibitors based on dithienylethenes and fulgimides

The synthesis, photochromic properties, inhibition of different HDACs and corresponding molecular dockings of photochromic inhibitors are described.

Localization and dynamics of the anticarcinogenic curcumin with GM1 and other miceller assemblies

Structural transitions involving shape changes play an important role in cellular physiology and enhance the bioavailability of the natural food like curcumin in surfactant aggregates. In this work, we have studied the localization, dynamics and stability of curcumin in various miceller assemblies using a combination of absorbance and fluorescence spectroscopic approaches. The measurements of absorption and fluorescence spectra of curcumin revealed that the nature of interactions of ionic and nonionic surfactants and the glycosphingolipid, GM₁ with curcumin is significantly different with surfactant concentrations. At low concentrations of SDS and the GM₁ the head group of SDS and GM₁ binds to the central β-diketone group of curcumin to form SDS-curcumin or GM₁-curcumin complexes. At high concentrations, both formed micelles with curcumin completely solubilized inside. Cucurmin is solubilized in the stern layer of SDS micelles. Compared to spherical micelles, rod shaped micelles allow more curcumin to bind through hydrophobic interactions indicated by higher absorption and fluorescence, enhanced partition coefficient and stability. Whereas curcumin associates with GM₁ micelles with lower partition coefficient, solubility and remain closer to aqueous phase decreasing its bioavailability and stability. While cucurmin is solubilized in the palisade layer of deoxycholate and octyl glucopyranoside micelles through the alkyl chains providing more hydrophobic microenvironment to curcumin with enhanced stability and bioavailability. Graphical abstract Schematic diagram of the two different types of detergent micelles and larger GM1 micelles.

Regorafenib: A novel tyrosine kinase inhibitor: A brief review of its therapeutic potential in the treatment of metastatic colorectal carcinoma and advanced gastrointestinal stromal tumors

Regorafenib is a novel oral multitargeted tyrosine kinase inhibitor having both antitumor and anti-angiogenic activities. Regorafenib was recently approved by US Food and Drug Administration in February 25, 2013 in the treatment for patients with advanced gastrointestinal stromal tumor and for the treatment of patients with metastatic colorectal carcinoma after disease progression or intolerance to imatinib mesylate and sunitinib therapy. Oral regorafenib demonstrates a high level of efficacy with acceptable tolerability with the 160 mg daily for 3 weeks followed by 1 week off schedule; a continuous schedule could be of interest. Hypertension, mucositis, hand foot skin reaction, diarrhea and asthenia are the most common side-effects. Regardless of these encouraging results, studies investigating, adjuvant and neoadjuvant settings are awaited, as well as trials using regorafenib in combination with chemotherapy or other targeted therapies. Clinical trials investigating regorafenib in other tumor types are ongoing.

Probing protein adsorption on a nanoparticle surface using second harmonic light scattering

A new application of second harmonic light scattering to probe protein physisorption on a gold nanoparticle surface in aqueous buffer is reported. The free energies of adsorption, the number of protein molecules adsorbed on the surface and the binding affinity of a moderate size protein, alcohol dehydrogenase (ADH), and a small protein, insulin, have been determined using the change in the second harmonic scattered light signal as a function of binding. Four different size gold nanoparticles from 15 to 60 nm were used to determine the effect of size on the free energy change, the affinity constant and the number of protein molecules adsorbed on the surface. All were shown to increase with an increase in size. The binding can be reversed by centrifugation, and the protein molecules can be desorbed quantitatively. The application of this method for studying thermodynamic parameters of weakly interacting biomolecules with nanoparticles for nanoparticle based diagnostic and therapeutic formulations is important.

A FACS Based Case Study on Two HbE-β Thalassaemia Members of a Family, Having Similar Mutational Background

In this report we have tried to explain the reasons behind the difference in the pattern of transfusion requirement between two members of a family with similar β-globin mutation. The father and younger son both are HbE-β, but the father never had transfusion, whereas the younger son takes transfusion monthly. Mother and the elder son are HbEE without any history of transfusion. β-globin mutations of all family members were determined by ARMS-PCR. These were reconfirmed by direct sequencing of β-globin gene. Father and younger son were found to be Cod 26 (G-A)/IVS 1-5 (G-C), whereas mother and elder son were found to be Cod 26 (G-A)/Cod 26 (G-A). XmnI sequencing also revealed that all members of the family were CC. Then, flow cytometry study of red blood cells (RBCs) was performed to measure the oxidative stress of the RBCs. This study was also done on the light and dense fractions of the RBC population of the father and younger son. It was seen that the younger son suffers severe oxidative stress, which can be explained by his higher transfusion requirement. From our work, we have established the importance of taking oxidative stress of RBCs into consideration to explain the clinical manifestation and progression of haemoglobin related diseases like thalassaemia.