Understanding Stability of Protein-Protein Complexes

For all living organisms, macromolecular interactions facilitate most of their natural functions. Alterations to macromolecular structures through mutations, can affect the stability of their interactions, which may lead to unfavourable phenotypes and disease. Presented here, are a number of computational methods aimed at uncovering the principles behind complex stability - as described by binding affinity and dissociation rate constants. Several factors are known to govern the stability of protein-protein interactions, however, no one factor dominates, and it is the synergistic effect of a number of contributions, which amount to the affinity, and stability of a complex. The characterization of complex stability can thus be presented as a two-fold problem; modelling the individual factors and modelling the synergistic effect of the combination of such individual factors. Using machine learning as a central framework, empirical functions are designed for estimating affinity, dissociation rates and the effects of mutations on these properties. The performance of all models is in turn benchmarked on experimental data available from the literature and carefully curated datasets. Firstly, a wild-type binding free energy prediction model is designed, composed of a diverse set of stability descriptors, which account for flexibility and conformational changes undergone by the complex in question. Similarly, models for estimating the effects of mutations on binding affinity are also designed and benchmarked in a community-wide blind trial. Emphasis here is on the detection of a small subset of mutations that are able to enhance the stability of two de novo protein drugs targeting the flu virus hemagglutinin. Probing further the determinants of stability, a set of descriptors that link hotspot residues with the off-rate of a complex are designed, and applied to models predicting changes in off-rate upon mutation. Finally, the relationship between the distribution of hotspots at protein interfaces, and the rate of dissociation of such interfaces, is investigated

Grouped periorbital comedones

Comedones (blackheads) grouped or closely packed in the periorbital area of the face, and not associated with acne vulgaris, have been described by Crocker (1884), Thin (1888), Morris (1911) and many others. The following investigation was undertaken in order to establish the incidence of grouped periorbital comedones in adults and observe what other conditions were present in persons having these skin lesions.peer-reviewe

Pro- and anti-inflammatory cytokines in threatened miscarriages

OBJECTIVE: The purpose of this study was to evaluate circulating and intracellular levels of Th1 and Th2 cytokines in women with threatenedmiscarriage (TM) and subsequent outcome. STUDY DESIGN: Plasma levels of tumor necrosis factor (TNF)-receptors 1 and 2, TNF , interferon gamma (IFN ), and interleukins (IL) -6 and -10 were measured by flow cytometric bead assays in 80 women with TM: 53 women with normal outcome and 27 women who miscarried. Fluorescent antibody labeling was also performed on whole blood in a subgroup of 27 women of TM: 16 women with normal outcome and 11 women who miscarried. RESULTS: Monocyte expression of TNF and circulating levels of TNF , IFN , IL-10, IL-6, and TNF-R1 were significantly lower, whereas circulating levels of TNF /IL-10, IFN /IL-10, and TNF /IL-6 ratios were significantly higher, in women with TM who subsequently miscarried, compared with the women with normal outcome. CONCLUSION: An increased Th1 type of immune response, which was similar to that observed in preterm delivery, was found in TM cases that were complicated by a subsequent miscarriage.peer-reviewe

Clinical interventions proposed by a pharmacist in the intensive care unit.

Patients admitted to the Intensive Care Unit (ICU) are at increased risk of adverse drug events due to underlying comorbidities, organ dysfunction and pharmacokinetic alterations in addition to being prescribed almost twice as many medications as patients in general hospital wards. The role of the pharmacist in this setting has developed considerably and includes working as a part of the multi-disciplinary team providing several clinical services. Locally, clinical pharmacy services were limited in ICU. Thus, the aim of this study was to assess the interventions of a pharmacist in ICU by quantifying and categorising drug-related problems (DRPs) identified by, and determining the frequency and type of clinical interventions suggested by a pharmacist introduced in ICU. The study was carried out over eight weeks in ICU of an acute general hospital in Malta, during which the pharmacist reviewed medication charts of patients admitted to ICU over the study period and identified DRPs. DRPs and suggested pharmaceutical interventions (PIs) were discussed with ICU clinicians or nurses depending on type of PI, and the outcome was recorded. All data was recorded in a previously validated, adapted, and piloted data collection tool. Data was classified into type of DRP and PI, therapeutic class, and outcome relating to acceptance and implementation of PIs. During the study period, medication charts of 124 ICU patients were reviewed. The pharmacist identified 161 DRPs in 54 patients and suggested a PI for each DRP. The most frequently identified DRP categories were 'administration related' (29%), 'supratherapeutic dosage' (20%) and 'drug monitoring' (18%). The most common categories of suggested PIs were 'dose adjustment' (34%) and 'administration optimisation' (29%). Antimicrobials (46%) and medications acting on the central nervous system (17%) were the therapeutic classes most frequently involved in DRPs. The ICU clinical team accepted and implemented 95% of PIs suggested by the pharmacist. This research demonstrated the value of introduction of a pharmacist within ICU. The high rate of accepted PIs concerning a wide range of DRPs demonstrate that advanced collaboration between a pharmacist and the ICU team is possible. The proposed clinical interventions by the pharmacist reflect the contribution of the pharmacist to the reduction of DRPs in critically ill patients, thus, optimising treatment for these patients

A possible hazard of splenectomy

The first case of splenectomy in St. Luke`s Hospital of a four months old infant is described. The infant died from a fulminating septicemia just over six weeks after splenectomy. Similar case studies indicated that fulminating infection occurs after splenectomy, particularly in infancy which could result fatal. In this regard, this study recommends that splenectomy should not be performed in the preschool child. Furthermore a careful follow-up of all splenectomised patients is advisable, by also treating any infection no matter how minor it may appear to be.peer-reviewe

Chemical determinants of occupational hypersensitivity pneumonitis

Background: Workplace inhalational exposures to low molecular weight (LMW) chemicals cause hypersensitivity pneumonitis (HP) as well as the more common manifestation of respiratory hypersensitivity, occupational asthma (OA). Aims: To explore whether chemical causation of HP is associated with different structural and physico-chemical determinants from OA. Methods: Chemical causes of human cases of HP and OA were identified from searches of peer-reviewed literature up to the end of 2011. Each chemical was categorised according to whether or not it had been the attributed cause of at least one case of HP. The predicted asthma hazard was determined for each chemical using a previously developed quantitative structure-activity relationship (QSAR) model. The chemicals in both sets were independently and ‘blindly’ analysed by an expert in mechanistic chemistry for a qualitative prediction of protein cross-linking potential and determination of lipophilicity (log Kow). Results: Ten HP causing chemicals were identified and had a higher median QSAR predicted asthma hazard than the control group of 101 OA causing chemicals (p < 0.005). Nine of ten HP causing chemicals were predicted to be protein cross-linkers compared to 24/92 controls (p<0.0001). The distributions of log Kow indicated higher values for the HP list (median 3.47) compared to controls (median 0.81) (p < 0.05). Conclusion: These findings suggest that chemicals capable of causing HP tend to have higher predicted asthma hazard, are more lipophilic and are more likely to be protein cross-linkers than those causing OA. Key words: hypersensitivity pneumonitis, occupational chemicals, occupational respiratory disease, toxic inhalatio

Investigation of systemic inflammatory response in first trimester pregnancy failure

Background: The contribution of local and systemic inflammation to the pathophysiology of sporadic first trimester miscarriages remains unclear. The objective of this study was to investigate the inflammatory response in the circulation of women presenting with first trimester miscarriage. Methods: Levels of tumour necrosis factor alpha (TNFa), TNF receptors 1 and 2, interferon gamma (IFNg), interleukin (IL)-6 and IL-10 were assayed using cytometric bead arrays in plasma samples from 29 euploid and 21 aneuploid missed miscarriages, 35 normal pregnant controls and 31 non-pregnant women (NPW). Whole blood flow cytometry was carried out with samples from 17 euploid and 16 aneuploid miscarriages, 18 pregnant controls and 13 NPW. Results: The plasma of women with euploid miscarriage contained significantly higher circulating levels of TNFa (P , 0.005), IFNg (P , 0.005), IL-6 (P , 0.005) and IL-10 (P , 0.01) than that of pregnant controls, irrespective of gestational age. Significantly (P , 0.05) higher TNF-R1 levels at 6–9 weeks, and significantly higher TNFa/IL-6 (P , 0.001) and significantly lower TNFa/IL-10 (P , 0.001) and IFNg/IL-10 (P , 0.001) ratios at 10–14 weeks, were also found in euploid miscarriage cases compared with pregnant controls. TNFa/IL-10 ratio in plasma was significantly (P , 0.05) lower in miscarriages with an abnormal karyotype than those with normal karyotype. Normal pregnant women had a significantly higher plasma level of IFNg (P , 0.01) and IFNg/IL-10 ratio (P , 0.005), a significantly (P , 0.005) lower TNF-R1 level, and a significant (P , 0.05) increase in stimulated TNFa in monocytes, compared with NPW. Conclusions: Our data confirm that there is an inflammatory reaction in normal pregnancy compared with the non-pregnant state, which may be disrupted during miscarriage.peer-reviewe