Membrane protein structure determination — The next generation Moraes, Isabel; Evans, Gwyndaf; Sanchez-Weatherby, Juan ...
Biochimica et biophysica acta. Biomembranes,
January 2014, 2014-Jan, 2014-01-00, 20140101, Letnik:
1838, Številka:
1
Journal Article
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The field of Membrane Protein Structural Biology has grown significantly since its first landmark in 1985 with the first three-dimensional atomic resolution structure of a membrane protein. Nearly ...twenty-six years later, the crystal structure of the beta2 adrenergic receptor in complex with G protein has contributed to another landmark in the field leading to the 2012 Nobel Prize in Chemistry. At present, more than 350 unique membrane protein structures solved by X-ray crystallography (http://blanco.biomol.uci.edu/mpstruc/exp/list, Stephen White Lab at UC Irvine) are available in the Protein Data Bank. The advent of genomics and proteomics initiatives combined with high-throughput technologies, such as automation, miniaturization, integration and third-generation synchrotrons, has enhanced membrane protein structure determination rate. X-ray crystallography is still the only method capable of providing detailed information on how ligands, cofactors, and ions interact with proteins, and is therefore a powerful tool in biochemistry and drug discovery. Yet the growth of membrane protein crystals suitable for X-ray diffraction studies amazingly remains a fine art and a major bottleneck in the field. It is often necessary to apply as many innovative approaches as possible. In this review we draw attention to the latest methods and strategies for the production of suitable crystals for membrane protein structure determination. In addition we also highlight the impact that third-generation synchrotron radiation has made in the field, summarizing the latest strategies used at synchrotron beamlines for screening and data collection from such demanding crystals. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding.
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•Overview of the most recent advances regarding the growth of membrane protein crystals•Rational design of new crystallization screens for membrane proteins•New automated method for dehydration of membrane proteins•High-throughput approach in seeding of membrane protein crystals•Recent developments in membrane protein structure determination
Dendritic side chains have been used to modify the binding environment in anthracene‐based synthetic carbohydrate receptors. Control of length, charge, and branching enabled the positioning of ...side‐chain carboxylate groups in such a way that they assisted in binding substrates rather than blocking the cavity. Conformational degeneracy in the dendrimers resulted in effective preorganization despite the flexibility of the system. Strong binding was observed to glucosammonium ions in water, with Ka values up to 7000 M−1. Affinities for uncharged substrates (glucose and N‐acetylglucosamine) were also enhanced, despite competition from solvent and the absence of electrostatic interactions.
Sticky branches: The carboxylate‐terminated side chains in a series of carbohydrate receptors contributed to binding if their length was just right. If they were too long, they blocked the cavity, but shorter variants could reach round to interact with polar groups on the substrate. Binding is favored by conformational degeneracy: if one carboxylate group moves away, another can take its place.
Biomimetic carbohydrate receptors (“synthetic lectins”) have potential as agents for biological research and medicine. However, although effective strategies are available for “all‐equatorial” ...carbohydrates (glucose, etc.), the recognition of other types of saccharide under natural (aqueous) conditions is less well developed. Herein we report a new approach based on a pyrene platform with polar arches extending from aryl substituents. The receptors are compatible with axially substituted carbohydrates, and also feature two identical binding sites, thus mimicking the multivalency observed for natural lectins. A variant with negative charges forms 1:2 host/guest complexes with aminosugars, with K1>3000 m−1 for axially substituted mannosamine, whereas a positively charged version binds the important α‐sialyl unit with K1≈1300 m−1.
Be my guests: Carbohydrate receptors featuring two equivalent binding sites were designed to target facially amphiphilic substrates. A version with anionic side chains favors aminosugars, whereas a cationic variant binds the biologically important α‐sialyl unit (as shown).
Conventional wisdom among policymakers in both the US and Europe holds that weak and failing states are the source of the world's most pressing security threats today. The international community's ...leadership sees such states as an existential threat as well, evidenced in Kofi Annan's 2004 claim that “our defenses are only as strong as their weakest links.” This is not surprising. The most destructive attack on the US in its history originated in one of the world's poorest countries. Deadly communicable diseases seem to constantly emerge from the world's poorest regions, and transnational crime appears to flourish in weakly governed states. However, as this book shows, our assumptions about the threats posed by failed and failing states are based on anecdotal arguments, not on a systematic empirical analysis that traces the connections between state failure and transnational security threats. This book uses an Index of State Weakness as a basis for its findings. The book provides coverage of five key security threats: terrorism, transnational crime, WMDs, pandemic diseases, and energy insecurity. The basic conclusions may seem surprising. While many threats do emerge in failed states, more often than not those states' manifold weaknesses create misery for only their own citizenry. In other words, the problems that flow from Liberia's failures are more typical than those that spread from Afghanistan. Moreover, many of threats originate farther up the chain, in wealthier and more stable countries like Russia, China, and Venezuela. And generic state weakness is not a good threat predictor. Cultural and regional particularities as well as the degree of global integration all influence the threat level. Just as importantly, our tendency to extrapolate an all-encompassing theory connecting weak states and international security threats from turmoil in the Middle East and Southwest Asia is insufficient. The book argues for complexity and nuance, and will force policymakers to rethink what they assume about state failure and transnational insecurity.
The human smile can convey both rewarding and affiliative social intent and thus has significant utility in politics, where the ability to bond with and reassure voters is vital to electoral success. ...We examine experimental evidence from the 2019 UK general election to investigate the influence of a politician's reward or affiliative smile on voter emotions. It was hypothesised that the winner's affiliative smile would engender positive affect across all partisan groups compared to the winner's reward smile display. Participants from a nationally representative sample were shown campaign footage containing both types of smiles from the leaders of the main competing political parties both before and after the election. Increases in happiness and affinity were revealed across all partisan groups when shown footage of the eventual winner's affiliative smile; at the same time, supporters of losing parties indicated a decrease in negative affect. Affinity has been shown to increase civic engagement. Thus, we conclude that affiliative smiles displayed by leading candidates during the campaign likely acted as a mechanism to align voter behaviour with the dominant political message.
Former United States President Ronald Reagan's use of media and his charismatic connection with viewers earned him the moniker "the great communicator". One aspect of his charisma, the influence of ...elicited laughter, during a highly critical 5-minute news story by CBS reporter Leslie Stahl during the 1984 US presidential election is examined here. Two experiments examining the effects of audience laughter on perceptions of charismatic leadership are reported. In the first experiment the effects of audience laughter in response to Reagan's comments were investigated. Here, Reagan's perceived warmth as an effective leader significantly diminished when strong laughter is removed, whereas perceptions of competence remained unaffected. The second study carried out on an older cohort replicated and extended the first in a pre-registered design by considering the perception of trait charisma. Here, the presence or absence of audience laughter did not affect judgements of charisma. Additionally, the affective response before, and then after, the presentation of the news story was measured. Emotions associated with a positive appraisal all decreased after being shown the news story while emotions associated negative appraisal all increased. However, only participant anger was significantly increased when audience laughter was removed. Taken together the findings of both studies converge on the fact that subtle changes in media presentation of political leaders can have a significant effect on viewers. The findings show that even after 40 years in office the social psychological effects of presidential charisma can still influence observers.
Abstract Influenza A and B, and many unrelated viruses including rhinovirus, RSV, adenovirus, metapneumovirus and coronavirus share the same seasonality, since these viral acute respiratory tract ...infections (vARIs) are much more common in winter than summer. Unfortunately, early investigations that used recycled “pedigree” virus strains seem to have led microbiologists to dismiss the common folk belief that vARIs often follow chilling. Today, incontrovertible evidence shows that ambient temperature dips and host chilling increase the incidence and severity of vARIs. This review considers four possible mechanisms, M1 - 4, that can explain this link: (M1) increased crowding in winter may enhance viral transmission; (M2) lower temperatures may increase the stability of virions outside the body; (M3) chilling may increase host susceptibility; (M4) lower temperatures or host chilling may activate dormant virions. There is little evidence for M1 or M2, which are incompatible with tropical observations. Epidemiological anomalies such as the repeated simultaneous arrival of vARIs over wide geographical areas, the rapid cessation of influenza epidemics, and the low attack rate of influenza within families are compatible with M4, but not M3 (in its simple form). M4 seems to be the main driver of seasonality, but M3 may also play an important role.
The 2016 United States presidential election was exceptional for many reasons; most notably the extreme division between supporters of Donald Trump and Hillary Clinton. In an election that turned ...more upon the character traits of the candidates than their policy positions, there is reason to believe that the non-verbal performances of the candidates influenced attitudes toward the candidates. Two studies, before Election Day, experimentally tested the influence of Trump’s micro-expressions of fear during his Republican National Convention nomination acceptance speech on how viewers evaluated his key leadership traits of competence and trustworthiness. Results from Study 1, conducted 3 weeks prior to the election, indicated generally positive effects of Trump’s fear micro-expressions on his trait evaluations, particularly when viewers were first exposed to his opponent, Clinton. In contrast, Study 2, conducted 4 days before Election Day, suggests participants had at that point largely established their trait perceptions and were unaffected by the micro-expressions.
Objective
On December 12, 2019, the United Kingdom's ruling Conservative Party called an election that put the country's 2016 “Brexit” referendum on leaving the European Union to the test. The ...divisive campaign and a polarized electorate culminated in large losses by opposition Labour and Liberal Democratic parties. Amid a polarized electorate, lingering questions arise as to whether the election results reflect more upon partisan ties or the respective party leaders' ability to emotionally connect with followers through their nonverbal behavior.
Methods
Using a unique pre‐registered design, this study considers the emotional response to leaders of the three major U.K. political parties in the week prior to the December 2019 election by drawing upon a national sample of 546 partisan participants. We examine self‐reported happiness, affinity, anger, and distress in response to reward and affiliative smiles as well as ambiguous facial displays in short videos shown without sound featuring Conservative Party leader Boris Johnson and his opponents Jeremy Corbyn (Labour Party) and Jo Swinson (Liberal Democratic Party).
Results
The findings of this pre‐registered study suggests partisan identity plays a powerful role in empathetic and counter‐empathetic responses to leader facial displays generally. Further analysis reveals a more nuanced response to the competing leaders’ facial displays with followers of all three parties responding to the different smiles in distinct manners.
Summary
This review seeks to explain three features of viral respiratory illnesses that have perplexed generations of virologists: (1) the seasonal timing of respiratory illness and the rapid ...response of outbreaks to weather, specifically temperature; (2) the common viruses causing respiratory illness worldwide, including year‐round disease in the Tropics; (3) the rapid arrival and termination of epidemics caused by influenza and other viruses. The inadequacy of the popular explanations of seasonality is discussed, and a simple hypothesis is proposed, called temperature dependent viral tropism (TDVT), that is compatible with the above features of respiratory illness. TDVT notes that viruses can spread more effectively if they moderate their pathogenicity (thereby maintaining host mobility) and suggests that endemic respiratory viruses accomplish this by developing thermal sensitivity within a range that supports organ‐specific viral tropism within the human body, whereby they replicate most rapidly at temperatures below body temperature. This can confine them to the upper respiratory tract and allow them to avoid infecting the lungs, heart, gut etc. Biochemical and tissue‐culture studies show that ‘wild’ respiratory viruses show such natural thermal sensitivity. The typical early autumn surge of colds and the occurrence of respiratory illness in the Tropics year‐round at intermediate levels are explained by the tendency for strains to adapt their thermal sensitivity to their local climate and season. TDVT has important practical implications for preventing and treating respiratory illness including Covid‐19. It is testable with many options for experiments to increase our understanding of viral seasonality and pathogenicity.
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