scholarly journals It's Better To Be Lucky Than Smart

2021 ◽  
Vol 90 (1) ◽  
Author(s):  
H.R. Kaback
Keyword(s):  
Energy Source ◽  
Active Transport ◽  
Experimental System ◽  
Membrane Vesicles ◽  
Solute Concentration ◽  
Annual Review ◽  
Publication Date ◽  
Experimental Conditions ◽  
Intact Cells ◽  
Transport Vesicles

Bacterial cytoplasmic membrane vesicles provide a unique experimental system for studying active transport. Vesicles are prepared by lysis of osmotically sensitized cells (i.e., protoplasts or spheroplasts) and comprise osmotically intact, unit-membrane-bound sacs that are approximately 0.5–1.0 μm in diameter and devoid of internal structure. Their metabolic activities are restricted to those provided by the enzymes of the membrane itself, and each vesicle is functional. The energy source for accumulation of a particular substrate can be determined by studying which compounds or experimental conditions drive solute accumulation, and metabolic conversion of the transported substrate or the energy source is minimal. These properties of the vesicle system constitute a considerable advantage over intact cells, as the system provides clear definition of the reactions involved in the transport process. This discussion is not intended as a general review but is concerned with respiration-dependent active transport in membrane vesicles from Escherichia coli. Emphasis is placed on experimental observations demonstrating that respiratory energy is converted primarily into work in the form of a solute concentration gradient that is driven by a proton electrochemical gradient, as postulated by the chemiosmotic theory of Peter Mitchell. Expected final online publication date for the Annual Review of Biochemistry, Volume 90 is June 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dynamics of Ecological Communities Following Current Retreat of Glaciers

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
Gentile Francesco Ficetola ◽  
Silvio Marta ◽  
Alessia Guerrieri ◽  
Mauro Gobbi ◽  
Roberto Ambrosini ◽  
...  
Keyword(s):  
Community Dynamics ◽  
Abiotic Factors ◽  
Empirical Studies ◽  
Experimental System ◽  
Theoretical Models ◽  
Glacier Retreat ◽  
Community Formation ◽  
Annual Review ◽  
Publication Date ◽  
Ecological Communities

Glaciers are retreating globally, and the resulting ice-free areas provide an experimental system for understanding species colonization patterns, community formation, and dynamics. The last several years have seen crucial advances in our understanding of biotic colonization after glacier retreats, resulting from the integration of methodological innovations and ecological theories. Recent empirical studies have demonstrated how multiple factors can speed up or slow down the velocity of colonization and have helped scientists develop theoretical models that describe spatiotemporal changes in community structure. There is a growing awareness of how different processes (e.g., time since glacier retreat, onset or interruption of surface processes, abiotic factors, dispersal, biotic interactions) interact to shape community formation and, ultimately, their functional structure through succession. Here, we examine how these studies address key theoretical questions about community dynamics and show how classical approaches are increasingly being combined with environmental DNA metabarcoding and functional trait analysis to document the formation of multitrophic communities, revolutionizing our understanding of the biotic processes that occur following glacier retreat. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 52 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Quantitative Surface-Enhanced Spectroscopy

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Ryan D. Norton ◽  
Hoa T. Phan ◽  
Stephanie N. Gibbons ◽  
Amanda J. Haes
Keyword(s):  
Raman Scattering ◽  
Annual Review ◽  
Publication Date ◽  
Experimental Conditions ◽  
Selection Rules ◽  
Surface Enhanced ◽  
Sers Detection ◽  
Raman Modes ◽  
Molecular Affinity ◽  
Quantitative Sers

Surface-enhanced Raman scattering (SERS), a powerful technique for trace molecular detection, depends on chemical and electromagnetic enhancements. While recent advances in instrumentation and substrate design have expanded the utility, reproducibility, and quantitative capabilities of SERS, some challenges persist. In this review, advances in quantitative SERS detection are discussed as they relate to intermolecular interactions, surface selection rules, and target molecule solubility and accessibility. After a brief introduction to Raman scattering and SERS, impacts of surface selection rules and enhancement mechanisms are discussed as they relate to the observation of activation and deactivation of normal Raman modes in SERS. Next, experimental conditions that can be used to tune molecular affinity to and density near SERS substrates are summarized and considered while tuning these parameters are conveyed. Finally, successful examples of quantitative SERS detection are discussed, and future opportunities are outlined. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 73 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

ABCA1 mediates high-affinity uptake of 25-hydroxycholesterol by membrane vesicles and rapid efflux of oxysterol by intact cells

2006 ◽  
Vol 291 (3) ◽  
pp. C490-C502 ◽  
Author(s):  
Shui-Pang Tam ◽  
Leo Mok ◽  
Giovanna Chimini ◽  
Monika Vasa ◽  
Roger G. Deeley
Keyword(s):  
Ldl Receptor ◽  
Membrane Vesicles ◽  
Wild Type ◽  
Experimental Conditions ◽  
Intact Cells ◽  
Hmg Coa Reductase ◽  
Human Embryonic Kidney Cells ◽  
Direct Demonstration ◽  
Coa Reductase

ATP Binding Cassette (ABC) transporter, ABCA1, plays a pivotal role in reverse cholesterol transport by mediating the cellular efflux of phospholipid and cholesterol. Studies using intact cells strongly suggest that ABCA1 acts as a phospholipid floppase, but there has been no direct demonstration that the protein is a primary active sterol transporter. Using membrane vesicles from insect Sf21 cells, we found that ABCA1 mediated ATP-dependent uptake of [3H]25-hydroxycholesterol with an apparent Km of 0.7 μM. Consistent with this high apparent affinity, expression of ABCA1 in human embryonic kidney cells both increased rapid efflux of 25-hydroxcholesterol and prevented oxysterol-mediated repression of low-density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase mRNAs. Comparison of wild-type and ABCA1−/− murine fibroblasts indicates that 25-hydroxycholesterol is effluxed ∼5-fold more rapidly by wild-type cells. In addition, the rate of efflux from the wild-type but not the ABCA1−/− fibroblasts is increased a further twofold by inducers of ABCA1 expression. Thus under the experimental conditions employed, endogenous ABCA1 is a major contributor to 25-hydroxycholesterol efflux from wild-type fibroblasts. Evidence from in vitro studies indicates that oxysterols are potent inducers of genes involved in cellular cholesterol efflux and metabolism, including the ABCA1 gene, and repressors of genes involved in cholesterol synthesis or uptake. Our observations raise the possibility that efflux of oxysterols by ABCA1 could contribute to a homeostatic mechanism, which both attenuates oxysterol-induced expression of its cognate gene and alleviates repression of genes encoding proteins, such as HMG-CoA reductase and LDL receptor.

Analysis of Tandem Repeat Protein Folding Using Nearest-Neighbor Models

2021 ◽  
Vol 50 (1) ◽  
Author(s):  
Mark Petersen ◽  
Doug Barrick
Keyword(s):  
Protein Folding ◽  
Tandem Repeat ◽  
Nearest Neighbor ◽  
Experimental System ◽  
Structural Features ◽  
Internal Symmetry ◽  
Statistical Thermodynamic ◽  
Annual Review ◽  
Publication Date ◽  
Repeat Proteins

Cooperativity is a hallmark of protein folding, but the thermodynamic origins of cooperativity are difficult to quantify. Tandem repeat proteins provide a unique experimental system to quantify cooperativity due to their internal symmetry and their tolerance of deletion, extension, and in some cases fragmentation into single repeats. Analysis of repeat proteins of different lengths with nearest-neighbor Ising models provides values for repeat folding (ΔGi) and inter-repeat coupling (Δ Gi-1, i). In this article, we review the architecture of repeat proteins and classify them in terms of Δ Gi and Δ Gi-1, i; this classification scheme groups repeat proteins according to their degree of cooperativity. We then present various statistical thermodynamic models, based on the 1D-Ising model, for analysis of different classes of repeat proteins. We use these models to analyze data for highly and moderately cooperative and noncooperative repeat proteins and relate their fitted parameters to overall structural features. Expected final online publication date for the Annual Review of Biophysics, Volume 50 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Bacterial Outer Membrane Vesicles: From Discovery to Applications

2021 ◽  
Vol 75 (1) ◽  
Author(s):  
Mariana G. Sartorio ◽  
Evan J. Pardue ◽  
Mario F. Feldman ◽  
M. Florencia Haurat
Keyword(s):  
Outer Membrane ◽  
Stress Responses ◽  
Current Knowledge ◽  
Cell Communication ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Multiple Roles ◽  
Annual Review ◽  
Publication Date ◽  
Cellular Components

Secretion of cellular components across the plasma membrane is an essential process that enables organisms to interact with their environments. Production of extracellular vesicles in bacteria is a well-documented but poorly understood process. Outer membrane vesicles (OMVs) are produced in gram-negative bacteria by blebbing of the outer membrane. In addition to their roles in pathogenesis, cell-to-cell communication, and stress responses, OMVs play important roles in immunomodulation and the establishment and balance of the gut microbiota. In this review, we discuss the multiple roles of OMVs and the current knowledge of OMV biogenesis. We also discuss the growing and promising biotechnological applications of OMV. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals Active Transport in Isolated Bacterial Membrane Vesicles

1972 ◽  
Vol 247 (1) ◽  
pp. 298-304 ◽  
Author(s):  
Steven A. Short ◽  
David C. White ◽  
H. Ronald Kaback
Keyword(s):  
Active Transport ◽  
Membrane Vesicles ◽  
Bacterial Membrane

scholarly journals Mechanisms of Active Transport in Isolated Bacterial Membrane Vesicles

1973 ◽  
Vol 248 (10) ◽  
pp. 3551-3565 ◽  
Author(s):  
Frank J. Lombardi ◽  
John P. Reeves ◽  
H. Ronald Kaback
Keyword(s):  
Active Transport ◽  
Membrane Vesicles ◽  
Bacterial Membrane

Endogenous Retroviruses Drive Resistance and Promotion of Exogenous Retroviral Homologs

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Elliott S. Chiu ◽  
Sue VandeWoude
Keyword(s):  
Immune Modulation ◽  
Viral Infections ◽  
Viral Evolution ◽  
Endogenous Retroviruses ◽  
Annual Review ◽  
Publication Date ◽  
Biological Functions ◽  
Self Tolerance ◽  
Vertebrate Hosts ◽  
Insight Into

Endogenous retroviruses (ERVs) serve as markers of ancient viral infections and provide invaluable insight into host and viral evolution. ERVs have been exapted to assist in performing basic biological functions, including placentation, immune modulation, and oncogenesis. A subset of ERVs share high nucleotide similarity to circulating horizontally transmitted exogenous retrovirus (XRV) progenitors. In these cases, ERV–XRV interactions have been documented and include ( a) recombination to result in ERV–XRV chimeras, ( b) ERV induction of immune self-tolerance to XRV antigens, ( c) ERV antigen interference with XRV receptor binding, and ( d) interactions resulting in both enhancement and restriction of XRV infections. Whereas the mechanisms governing recombination and immune self-tolerance have been partially determined, enhancement and restriction of XRV infection are virus specific and only partially understood. This review summarizes interactions between six unique ERV–XRV pairs, highlighting important ERV biological functions and potential evolutionary histories in vertebrate hosts. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 9 is February 16, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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