Key message
European beech showed low resistance but high resilience in radial growth after an extreme late frost event. Site-specific growth reductions correlated with absolute minimum temperature ...in May
.
Late spring frost events occurring after the early leaf unfolding (“false spring”) can result in severe leaf damages in deciduous trees. With climate warming, such damages may occur more frequently due to an earlier start of the growing season. While affected, mature trees usually survive, but radial and height growth after the late frost has rarely been quantified in relation to the magnitude of the frost events. The effects of a severe late frost event in the early May 2011, following a warm spring and early bud break, was quantified for European beech (
Fagus sylvatica
L.) at 7 forest stands in Bavaria, Germany. Resistance and resilience of tree growth were quantified based on tree-ring widths of 135 trees. Resistance to the late frost event (comparing tree-ring width in the frost year with the previous 5 years) was on average reduced by 46%. Resistance was positively correlated with May minimum temperature at the study sites, indicating a relationship between growth reduction and frost severity. Partial least-square linear models based on monthly climate data (precipitation, temperature, potential evapotranspiration, and the Standardized Precipitation Evapotranspiration Index) could not explain the growth reduction in 2011, thereby providing evidence for the importance of frost damages on annual growth.
F. sylvatica
showed high resilience after the frost year, with tree-ring widths in the subsequent years being comparable to the previous years. This study suggests that frost events may strongly reduce growth of
F. sylvatica
in the event year, but that carry-over effects on the radial growth of subsequent years are not likely.
In many parts of the world, especially in the temperate regions of Europe and North-America, accelerated tree growth rates have been observed over the last decades. This widespread phenomenon is ...presumably caused by a combination of factors like atmospheric fertilization or changes in forest structure and/or management. If not properly acknowledged in the calibration of tree-ring based climate reconstructions, considerable bias concerning amplitudes and trends of reconstructed climatic parameters might emerge or low frequency information is lost. Here we present a simple but effective, data-driven approach to remove the recent non-climatic growth increase in tree-ring data. Accounting for the no-analogue calibration problem, a new hydroclimatic reconstruction for northern-central Europe revealed considerably drier conditions during the medieval climate anomaly (MCA) compared with standard reconstruction methods and other existing reconstructions. This demonstrates the necessity to account for fertilization effects in modern tree-ring data from affected regions before calibrating reconstruction models, to avoid biased results.
Glycosylation patterns in antibodies critically determine biological and physical properties but their precise control is a significant challenge in biology and biotechnology. We describe herein the ...optimization of an endoglycosidase‐catalyzed glycosylation of the best‐selling biotherapeutic Herceptin, an anti‐HER2 antibody. Precise MS analysis of the intact four‐chain Ab heteromultimer reveals nonspecific, non‐enzymatic reactions (glycation), which are not detected under standard denaturing conditions. This competing reaction, which has hitherto been underestimated as a source of side products, can now be minimized. Optimization allowed access to the purest natural form of Herceptin to date (≥90 %). Moreover, through the use of a small library of sugars containing non‐natural functional groups, Ab variants containing defined numbers of selectively addressable chemical tags (reaction handles at Sia C1) in specific positions (for attachment of cargo molecules or “glycorandomization”) were readily generated.
You're the one that I want: The “blockbuster” antibody Herceptin was accessed with natural glycosylation through chemoenzymatic construction coupled with MS of the intact antibody (see picture). Herceptin was obtained with high purity (>90 %) when nonspecific, non‐enzymatic reactions (glycation) revealed by precise MS analysis were minimized. Glycosylation with unnatural sugars bearing tags also enabled the site‐selective attachment of cargo.
Sample purity is central to in vitro studies of protein function and regulation, and to the efficiency and success of structural studies using techniques such as x-ray crystallography and ...cryo-electron microscopy (cryo-EM). Here, we show that mass photometry (MP) can accurately characterize the heterogeneity of a sample using minimal material with high resolution within a matter of minutes. To benchmark our approach, we use negative stain electron microscopy (nsEM), a popular method for EM sample screening. We include typical workflows developed for structure determination that involve multi-step purification of a multi-subunit ubiquitin ligase and chemical cross-linking steps. When assessing the integrity and stability of large molecular complexes such as the proteasome, we detect and quantify assemblies invisible to nsEM. Our results illustrate the unique advantages of MP over current methods for rapid sample characterization, prioritization and workflow optimization.
The diversity of stereochemical isomers present in glycans and glycoconjugates poses a formidable challenge for comprehensive structural analysis. Typically, sophisticated mass spectrometry ...(MS)‐based techniques are used in combination with chromatography or ion‐mobility separation. However, coexisting structurally similar isomers often render an unambiguous identification impossible. Other powerful techniques such as gas‐phase infrared (IR) spectroscopy have been limited to smaller glycans, since conformational flexibility and thermal activation during the measurement result in poor spectral resolution. This limitation can be overcome by using cold‐ion spectroscopy. The vibrational fingerprints of cold oligosaccharide ions exhibit a wealth of well‐resolved absorption features that are diagnostic for minute structural variations. The unprecedented resolution of cold‐ion spectroscopy coupled with tandem MS may render this the key technology to unravel complex glycomes.
Fingerprints, please! The diversity of stereochemical isomers present in glycans poses a formidable challenge for comprehensive structural analysis. Cold‐ion spectroscopy has the potential to serve as a powerful method to disentangle the detailed structures of oligosaccharides. Even for minute structural variations of isomeric glycans, the remarkable resolving power of this technique provides highly diagnostic absorption patterns—a true spectral fingerprint.
Native-like trimers of the SOSIP design are being developed as immunogens in human immunodeficiency virus type 1 (HIV-1) vaccine development programs. These trimers display the epitopes for multiple ...broadly neutralizing antibodies (bNAbs) but can also expose binding sites for some types of nonneutralizing antibodies (non-NAbs). Among the latter are epitopes in the gp120 V3 region that are highly immunogenic when SOSIP trimers are evaluated in animal models. It is presently uncertain whether antibodies against V3 can interfere with the induction of NAbs, but there are good arguments in favor of suppressing such "off-target" immune responses. Accordingly, we have assessed how to minimize the exposure of V3 non-NAb epitopes and thereby reduce their immunogenicity by introducing
-glycans within the V3 region of BG505 SOSIP trimers. We found that inserting glycans at positions 306 and 314 (termed M1 and M7) markedly reduced V3 antigenicity while improving the presentation of trimer apex bNAb epitopes. Both added glycans were shown to be predominantly of the Man
GlcNAc
form. The additional introduction of the E64K ground-state stabilizing substitution markedly reduced or ablated soluble CD4 (sCD4) induction of non-NAb epitopes in V3 and/or associated with the coreceptor binding site. When a V3 glycan- and E64K-modified trimer variant, BG505 SOSIP.664-E64K.M1M7, was tested in rabbits, V3 immunogenicity was eliminated while the autologous NAb response was unchanged.
Trimeric proteins are being developed for future HIV-1 vaccine trials in humans, with the goal of eliciting broadly active neutralizing antibodies (NAbs) that are active against a wide variety of circulating strains. In animal models, the present generation of native-like trimer immunogens, exemplified by the BG505 SOSIP.664 construct, induces narrow-specificity antibodies against the neutralization-resistant (tier-2), sequence-matched virus and more broadly active antibodies against sequence-divergent atypically neutralization-sensitive (tier-1) viruses. A concern in the trimer immunogen design field has been whether the latter off-target antibodies might interfere with the induction of the more desired responses to tier-2 epitopes. Here, we have inserted two glycans into the dominant site for tier-1 NAbs, the gp120 V3 region, to block the induction of off-target antibodies. We characterized the new trimers, tested them as immunogens in rabbits, and found that the blocking glycans eliminated the induction of tier-1 NAbs to V3-epitopes.
The mitochondrial amidoxime reducing component (mARC) is a human molybdoenzyme known to catalyze the reduction of various N-oxygenated substrates. The physiological function of mARC enzymes, however, ...remains unknown. In this study, we examine the reduction of hydrogen peroxide (H2O2) by the human mARC1 and mARC2 enzymes. Furthermore, we demonstrate an increased sensitivity toward H2O2 for HEK-293T cells with an MTARC1 knockout, which implies a role of mARC enzymes in the cellular response to oxidative stress. H2O2 is a reactive oxygen species (ROS) formed in all living cells involved in many physiological processes. Furthermore, H2O2 constitutes the first mARC substrate without a nitrogen–oxygen bond, implying that mARC enzymes may have a substrate spectrum going beyond the previously examined N-oxygenated compounds.
Fucose is an essential deoxysugar that is found in a wide range of biologically relevant glycans and glycoconjugates. A recurring problem in mass spectrometric analyses of fucosylated glycans is the ...intramolecular migration of fucose units, which can lead to erroneous sequence assignments. This migration reaction is typically assigned to activation during collision‐induced dissociation (CID) in tandem mass spectrometry (MS). In this work, we utilized cold‐ion spectroscopy and show for the first time that fucose migration is not limited to fragments obtained in tandem MS and can also be observed in intact glycan ions. This observation suggests a possible low‐energy barrier for this transfer reaction and generalizes fucose migration to an issue that may universally occur in any type of mass spectrometry experiment.
Sweet talk: Fucose migration is a recurring problem in tandem mass spectrometric analyses of protonated glycans and leads to misleading fragment ions. So far, fucose migration has been associated with fragmentation during collision‐induced dissociation (CID). However, results from cold‐ion infrared spectroscopy show that fucose migration is not strictly limited to fragments obtained in tandem mass spectrometry and occurs in intact ions as well.
Human serum IgG contains multiple glycoforms which exhibit a range of binding properties to effector molecules such as cellular Fc receptors. Emerging knowledge of how the Fc glycans contribute to ...the antibody structure and effector functions has opened new avenues for the exploitation of defined antibody glycoforms in the treatment of diseases. Here, we review the structure and activity of antibody glycoforms and highlight developments in antibody glycoengineering by both the manipulation of the cellular glycosylation machinery and by chemoenzymatic synthesis. We discuss wide ranging applications of antibody glycoengineering in the treatment of cancer, autoimmunity and inflammation. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.
•IgG glycosylation impacts antibody effector function.•Modulation of antibody glycosylation has therapeutic potential.•Antibody glycoforms exhibit anti- and pro-inflammatory properties.
Transmission of hemorrhagic fever New World arenaviruses from their rodent reservoirs to human populations poses substantial public health and economic dangers. These zoonotic events are enabled by ...the specific interaction between the New World arenaviral attachment glycoprotein, GP1, and cell surface human transferrin receptor (hTfR1). Here, we present the structural basis for how a mouse-derived neutralizing antibody (nAb), OD01, disrupts this interaction by targeting the receptor-binding surface of the GP1 glycoprotein from Junín virus (JUNV), a hemorrhagic fever arenavirus endemic in central Argentina. Comparison of our structure with that of a previously reported nAb complex (JUNV GP1–GD01) reveals largely overlapping epitopes but highly distinct antibody-binding modes. Despite differences in GP1 recognition, we find that both antibodies present a key tyrosine residue, albeit on different chains, that inserts into a central pocket on JUNV GP1 and effectively mimics the contacts made by the host TfR1. These data provide a molecular-level description of how anti-bodies derived from different germline origins arrive at equivalent immunological solutions to virus neutralization.
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