Structure and dynamics of the lipid modifications of a transmembrane α-helical peptide determined by 2H solid-state NMR spectroscopy

AbstractThe fusion of biological membranes is mediated by integral membrane proteins with α-helical transmembrane segments. Additionally, those proteins are often modified by the covalent attachment of hydrocarbon chains. Previously, a series of de novo designed α-helical peptides with mixed Leu/Val sequences was presented, mimicking fusiogenically active transmembrane segments in model membranes (Hofmann et al., Proc. Natl. Acad. Sci. USA 101 (2004) 14776–14781). From this series, we have investigated the peptide LV16 (KKKW LVLV LVLV LVLV LVLV KKK), which was synthesized featuring either a free N-terminus or a saturated N-acylation of 2, 8, 12, or 16 carbons. We used 2H and 31P NMR spectroscopy to investigate the structure and dynamics of those peptide lipid modifications in POPC and DLPC bilayers and compared them to the hydrocarbon chains of the surrounding membrane. Except for the C2 chain, all peptide acyl chains were found to insert well into the membrane. This can be explained by the high local lipid concentrations the N-terminal lipid chains experience. Further, the insertion of these peptides did not influence the membrane structure and dynamics as seen from the 2H and 31P NMR data. In spite of the fact that the longer acyl chains insert into the membrane, they do not adapt their lengths to the thickness of the bilayer. Even the C16 lipid chain on the peptide, which could match the length of the POPC palmitoyl chain, exhibited lower order parameters in the upper chain, which get closer and finally reach similar values in the lower chain region. 2H NMR square law plots reveal motions of slightly larger amplitudes for the peptide lipid chains compared to the surrounding phospholipids. In spite of the significantly different chain lengths of the acylations, the fraction of gauche defects in the inserted chains is constant

Skalenhandbuch zur Dokumentation der Erhebungsinstrumente

Dies in eine aktualisierte Version von: https://doi.org/10.18452/3125 - Grund der Aktualisierung: In der FDZ-Version der Daten des IQB-LV 2012 wurde eine Änderung im Lehrkräftedatensatz vorgenommen. Die folgenden Variablen wurden hinzugefügt, um eine Replikation des Ergebnisberichts zu ermöglichen (Kapitel 12, Tabelle 12.1 und Tabelle 12.2): lalter_re, mathe_ind, bio_ind, che_ind, phy_ind. Dies wurde in der vorliegenden Version des SHB des LV 12 aktualisiert.Das Skalenhandbuch dokumentiert die Erhebungsinstrumente, die im IQB-Ländervergleich 2012 in der Sekundarstufe I eingesetzt wurden. Dies umfasst die Testinstrumente zur Erfassung der Kompetenzen in den Fächern Mathematik, Biologie, Chemie und Physik sowie die Fragebögen der Schüler*innen, der Lehrkräfte und der Schulleitungen. Der IQB-Ländervergleich dient einem systematischen Vergleich der Länder der Bundesrepublik Deutschland mit Blick auf die in den Bildungsstandards für die naturwissenschaftlichen Fächer und Mathematik beschriebenen Kompetenzen am Ende der Sekundarstufe I

Studying interactions among anthropogenic stressors in freshwater ecosystems: A systematic review of 2396 multiple‐stressor experiments

Understanding the interactions among anthropogenic stressors is critical for effective conservation and management of ecosystems. Freshwater scientists have invested considerable resources in conducting factorial experiments to disentangle stressor interactions by testing their individual and combined effects. However, the diversity of stressors and systems studied has hindered previous syntheses of this body of research. To overcome this challenge, we used a novel machine learning framework to identify relevant studies from over 235,000 publications. Our synthesis resulted in a new dataset of 2396 multiple‐stressor experiments in freshwater systems. By summarizing the methods used in these studies, quantifying trends in the popularity of the investigated stressors, and performing co‐occurrence analysis, we produce the most comprehensive overview of this diverse field of research to date. We provide both a taxonomy grouping the 909 investigated stressors into 31 classes and an open‐source and interactive version of the dataset (https://jamesaorr.shinyapps.io/freshwater‐multiple‐stressors/). Inspired by our results, we provide a framework to help clarify whether statistical interactions detected by factorial experiments align with stressor interactions of interest, and we outline general guidelines for the design of multiple‐stressor experiments relevant to any system. We conclude by highlighting the research directions required to better understand freshwater ecosystems facing multiple stressors

Experimental comparative study of the histotoxicity of poly(lactic-co-glycolic acid) copolymer and poly(lactic-co-glycolic acid)-poly(isoprene) blend

Current treatments of craniosynostosis rely on the application of metal springs for cranial bone deviation. However, those metal springs demand a second surgical procedure for their removal. An attractive alternative would be the substitution of metal for bioresorbable polymers in the composition of the springs. The addition of poly(isoprene), PI, to poly(lactic-co-glycolic acid), PLGA, produces a polymeric blend with partial miscibility and distinct mechanical behavior that may benefit the patient recover. It is necessary to compare the histotoxicity of PLGA/PI to that presented by PLGA. In order to verify the histological behavior of the blend, 46 male Wistar rats (Rattus norvegicus, albino strain) underwent implantation of PLGA or PLGA/PI in the skull and were allocated into subgroups by timing of euthanasia (15, 30, 60, or 90 days). After euthanasia, the skull was removed and the histotoxicity was assessed histopathologically. The PLGA/PI blend showed greater histotoxicity in animals euthanized at 60 days, although in this period the histotoxicity of the PLGA/PI blend was similar to that of the PLGA copolymer at 15 days. Despite the instability of histological response, presented in different periods of observation, the results obtained in long-term show that the material has high potential for studies in craniosynostosis treatment

Remote detection of invasive alien species

The spread of invasive alien species (IAS) is recognized as the most severe threat to biodiversity outside of climate change and anthropogenic habitat destruction. IAS negatively impact ecosystems, local economies, and residents. They are especially problematic because once established, they give rise to positive feedbacks, increasing the likelihood of further invasions and spread. The integration of remote sensing (RS) to the study of invasion, in addition to contributing to our understanding of invasion processes and impacts to biodiversity, has enabled managers to monitor invasions and predict the spread of IAS, thus supporting biodiversity conservation and management action. This chapter focuses on RS capabilities to detect and monitor invasive plant species across terrestrial, riparian, aquatic, and human-modified ecosystems. All of these environments have unique species assemblages and their own optimal methodology for effective detection and mapping, which we discuss in detail

An Overview of 9/11 Experiences and Respiratory and Mental Health Conditions among World Trade Center Health Registry Enrollees

http://deepblue.lib.umich.edu/bitstream/2027.42/61276/1/farfel m, digrande l, brackbill r, galea s, overview of 9-11 experiences and respiratory and mental haelth conditions.pd

CHARACTERIZATION AND DATING OF ARCHAEOLOGICAL EXCAVATED HUMAN BONE FROM JORDAN BY HIGH-RESOLUTION 31P AND 14C NMR AND FOURIER TRANSFORMATION INFRARED

Solid-State Nuclear Magnetic Resonance (SS-NMR) and Attenuated Total Reflection Fourier Transformation Infrared (ATR-FTIR) spectroscopy have excellent measurement performance for both organic and inorganic parts of bone or dental dentin. Solid-State Magic-Angle Spinning Nuclear Magnetic Resonance (SS-MAS-NMR) spectroscopy is an effective and constructive method for classifying samples, whether they are new or old. The objectives of this study include finding a new method for dating bone by SS-MAS-NMR and ATR-FTIR studies of old bone, supported by absolute dating of radioactive carbon isotopes. The specific objectives can be addressed by measuring the decomposition factor of the organic fraction in ancient bones and dentin in modern teeth, which are most similar to bones in terms of chemical composition, to arrive at a new time formula for the dating method. Eight old samples and one fresh tooth sample were taken for comparison. The method studied will be established as a new tool for characterizing ancient bone samples and detecting hydroxyl in bone minerals by SS-MAS-NMR