Table Of Contents Page, PNAS Volume 107, Number 15
This Week in PNAS
Letters (Online Only)
Commentaries
Atmospheric Chemistry Special Feature (free online)
Introduction
Research Articles
This study has used proton transfer reaction-mass spectrometry (PTR-MS) for direct
air analyses of volatile products resulting from the reactions of ozone with human
skin lipids. An initial series of small-scale in vitro and in vivo experiments were
...
This study shows that residual nicotine from tobacco smoke sorbed to indoor surfaces
reacts with ambient nitrous acid (HONO) to form carcinogenic tobacco-specific nitrosamines
(TSNAs). Substantial levels of TSNAs were measured on surfaces inside a smoker’...
In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible
for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide.
After polar sunrise, air masses enriched in reactive bromine cover areas of ...
The primary ozone loss process in the cold polar lower stratosphere hinges on chlorine
monoxide (ClO) and one of its dimers, chlorine peroxide (ClOOCl). Recently, analyses
of atmospheric observations have suggested that the equilibrium constant, Keq, ...
Recent field observations have shown that the atmospheric plumes of quiescently degassing
volcanoes are chemically very active, pointing to the role of chemical cycles involving
halogen species and heterogeneous reactions on aerosol particles that have ...
Simulations show that photodissociation of methyl hydroperoxide, CH3OOH, on water clusters produces a surprisingly wide range of products on a subpicosecond
time scale, pointing to the possibility of complex photodegradation pathways for organic
peroxides ...
Soot particles produced by incomplete combustion processes are one of the major components
of urban air pollution. Chemistry at their surfaces lead to the heterogeneous conversion
of several key trace gases; for example NO2 interacts with soot and is ...
A laser flash photolysis–resonance fluorescence technique has been employed to measure
rate coefficients and physical vs. reactive quenching branching ratios for O(1D) deactivation by three potent greenhouse gases, SO2F2(k1), NF3(k2), and SF5CF3(k3). In ...
Inorganic salts in marine aerosols play an active role in atmospheric chemistry, particularly
in coastal urban regions. The study of the interactions of these ions with water molecules
at the aqueous surface helps to elucidate the role of inorganic ...
Molecular beam scattering experiments are used to investigate reactions of SO2 at the surface of a molten alkali carbonate eutectic at 683 K. We find that two-thirds
of the SO2 molecules that thermalize at the surface of the melt are converted to gaseous ...
A number of recent studies have shown that iron dissolution in Fe-containing dust
aerosol can be linked to source material (mineral or anthropogenic), mineralogy, and
iron speciation. All of these factors need to be incorporated into atmospheric chemistry
...
We present laboratory studies and field observations that explore the role of aminium
salt formation in atmospheric nanoparticle growth. These measurements were performed
using the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) and ...
Isoprene is a significant source of atmospheric organic aerosol; however, the oxidation
pathways that lead to secondary organic aerosol (SOA) have remained elusive. Here,
we identify the role of two key reactive intermediates, epoxydiols of isoprene (...
New particle formation in the atmosphere is an important parameter in governing the
radiative forcing of atmospheric aerosols. However, detailed nucleation mechanisms
remain ambiguous, as laboratory data have so far not been successful in explaining
...
Oceans cover over two-thirds of the Earth’s surface, and the particles emitted to
the atmosphere by waves breaking on sea surfaces provide an important contribution
to the planetary albedo. During the International Chemistry Experiment in the Arctic
LOwer ...
Primary organic aerosol (POA) and associated vapors can play an important role in
determining the formation and properties of secondary organic aerosol (SOA). If SOA
and POA are miscible, POA will significantly enhance SOA formation and some POA vapor
...
Yields of β-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from
OH radical-initiated reactions of C9-C15 2-methyl-1-alkenes in the presence of NOx were measured by using a thermal desorption particle beam mass spectrometer ...
Organonitrates (ON) are important products of gas-phase oxidation of volatile organic
compounds in the troposphere; some models predict, and laboratory studies show, the
formation of large, multifunctional ON with vapor pressures low enough to partition
...
An understanding of the gas/particle-phase partitioning of semivolatile compounds
is critical in determining atmospheric aerosol formation processes and growth rates,
which in turn affect global climate and human health. The Study of Organic Aerosol
at ...
This study examines the sensitivity in predicted levels of atmospheric organic particulate
matter (Mo, μg m-3) as those levels may potentially be affected by changes in relative humidity and
temperature. In a given system, for each partitioning compound, ...
In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal
diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process
not previously considered to occur in water-restricted environments. In this ...
Cirrus clouds are ubiquitous in the tropical tropopause region and play a major role
in the Earth’s climate. Any changes to cirrus abundance due to natural or anthropogenic
influences must be considered to evaluate future climate change. The detailed ...
This study focuses on the retrieval of the normalized mass absorption cross section
(MAC) of soot using theoretical calculations that incorporate new measurements of
the optical properties of organic carbon (OC) intrinsic to fresh diesel soot. Intrinsic
...
Secondary organic aerosol (SOA) comprises a significant portion of atmospheric particular
matter. The impact of particular matter on both human health and global climate has
long been recognized. Despite its importance, there are still many unanswered ...
Physical Sciences
Applied Mathematics
The rapid accumulation of gene expression data has offered unprecedented opportunities
to study human diseases. The National Center for Biotechnology Information Gene Expression
Omnibus is currently the largest database that systematically documents the ...
Applied Physical Sciences
Deposition of high-κ dielectrics onto graphene is of significant challenge due to the difficulties of
nucleating high quality oxide on pristine graphene without introducing defects into
the monolayer of carbon lattice. Previous efforts to deposit high-κ ...
We describe an optical method capable of tracking a single fluorescent molecule with
a flexible choice of high spatial accuracy (∼10–20 nm standard deviation or ∼20–40 nm
full-width-at-half-maximum) and temporal resolution (< 1 ms). The fluorescence ...
Chemistry
The primary ozone loss process in the cold polar lower stratosphere hinges on chlorine
monoxide (ClO) and one of its dimers, chlorine peroxide (ClOOCl). Recently, analyses
of atmospheric observations have suggested that the equilibrium constant, Keq, ...
Simulations show that photodissociation of methyl hydroperoxide, CH3OOH, on water clusters produces a surprisingly wide range of products on a subpicosecond
time scale, pointing to the possibility of complex photodegradation pathways for organic
peroxides ...
A laser flash photolysis–resonance fluorescence technique has been employed to measure
rate coefficients and physical vs. reactive quenching branching ratios for O(1D) deactivation by three potent greenhouse gases, SO2F2(k1), NF3(k2), and SF5CF3(k3). In ...
Inorganic salts in marine aerosols play an active role in atmospheric chemistry, particularly
in coastal urban regions. The study of the interactions of these ions with water molecules
at the aqueous surface helps to elucidate the role of inorganic ...
Molecular beam scattering experiments are used to investigate reactions of SO2 at the surface of a molten alkali carbonate eutectic at 683 K. We find that two-thirds
of the SO2 molecules that thermalize at the surface of the melt are converted to gaseous ...
Isoprene is a significant source of atmospheric organic aerosol; however, the oxidation
pathways that lead to secondary organic aerosol (SOA) have remained elusive. Here,
we identify the role of two key reactive intermediates, epoxydiols of isoprene (...
New particle formation in the atmosphere is an important parameter in governing the
radiative forcing of atmospheric aerosols. However, detailed nucleation mechanisms
remain ambiguous, as laboratory data have so far not been successful in explaining
...
Primary organic aerosol (POA) and associated vapors can play an important role in
determining the formation and properties of secondary organic aerosol (SOA). If SOA
and POA are miscible, POA will significantly enhance SOA formation and some POA vapor
...
Yields of β-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from
OH radical-initiated reactions of C9-C15 2-methyl-1-alkenes in the presence of NOx were measured by using a thermal desorption particle beam mass spectrometer ...
Organonitrates (ON) are important products of gas-phase oxidation of volatile organic
compounds in the troposphere; some models predict, and laboratory studies show, the
formation of large, multifunctional ON with vapor pressures low enough to partition
...
An understanding of the gas/particle-phase partitioning of semivolatile compounds
is critical in determining atmospheric aerosol formation processes and growth rates,
which in turn affect global climate and human health. The Study of Organic Aerosol
at ...
In aqueous solution, aldehydes, and to a lesser extent ketones, hydrate to form geminal
diols. We investigate the hydration of methylglyoxal (MG) in the gas phase, a process
not previously considered to occur in water-restricted environments. In this ...
High level ab initio calculations at the MP2/cc-pVTZ, CCSD(T)/cc-pVTZ, and CASSCF(6,6)/cc-pVTZ
levels were performed to investigate geometries and energies of superelectrophilic
diprotonated, and dimethylated molecular chlorine () and bromine () ...
Engineering
Despite substantial size variations, proportions of the developing body plan are maintained
with a remarkable precision. Little is known about the mechanisms that ensure this
adaptation (scaling) of pattern with size. Most models of patterning by ...
Environmental Sciences
This study has used proton transfer reaction-mass spectrometry (PTR-MS) for direct
air analyses of volatile products resulting from the reactions of ozone with human
skin lipids. An initial series of small-scale in vitro and in vivo experiments were
...
This study shows that residual nicotine from tobacco smoke sorbed to indoor surfaces
reacts with ambient nitrous acid (HONO) to form carcinogenic tobacco-specific nitrosamines
(TSNAs). Substantial levels of TSNAs were measured on surfaces inside a smoker’...
In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible
for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide.
After polar sunrise, air masses enriched in reactive bromine cover areas of ...
Recent field observations have shown that the atmospheric plumes of quiescently degassing
volcanoes are chemically very active, pointing to the role of chemical cycles involving
halogen species and heterogeneous reactions on aerosol particles that have ...
Soot particles produced by incomplete combustion processes are one of the major components
of urban air pollution. Chemistry at their surfaces lead to the heterogeneous conversion
of several key trace gases; for example NO2 interacts with soot and is ...
A number of recent studies have shown that iron dissolution in Fe-containing dust
aerosol can be linked to source material (mineral or anthropogenic), mineralogy, and
iron speciation. All of these factors need to be incorporated into atmospheric chemistry
...
We present laboratory studies and field observations that explore the role of aminium
salt formation in atmospheric nanoparticle growth. These measurements were performed
using the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) and ...
Isoprene is a significant source of atmospheric organic aerosol; however, the oxidation
pathways that lead to secondary organic aerosol (SOA) have remained elusive. Here,
we identify the role of two key reactive intermediates, epoxydiols of isoprene (...
New particle formation in the atmosphere is an important parameter in governing the
radiative forcing of atmospheric aerosols. However, detailed nucleation mechanisms
remain ambiguous, as laboratory data have so far not been successful in explaining
...
Yields of β-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from
OH radical-initiated reactions of C9-C15 2-methyl-1-alkenes in the presence of NOx were measured by using a thermal desorption particle beam mass spectrometer ...
This study examines the sensitivity in predicted levels of atmospheric organic particulate
matter (Mo, μg m-3) as those levels may potentially be affected by changes in relative humidity and
temperature. In a given system, for each partitioning compound, ...
Secondary organic aerosol (SOA) comprises a significant portion of atmospheric particular
matter. The impact of particular matter on both human health and global climate has
long been recognized. Despite its importance, there are still many unanswered ...
Geology
A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon
isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused
by eruptions of continental flood basalt provinces. However, the necessary serial
...
View related content:
Mass extinctions of life and catastrophic flood basalt volcanism
The “hydraulic city” of Angkor, the capitol of the Khmer Empire in Cambodia, experienced
decades-long drought interspersed with intense monsoons in the fourteenth and fifteenth
centuries that, in combination with other factors, contributed to its eventual ...
Geophysics
Oceans cover over two-thirds of the Earth’s surface, and the particles emitted to
the atmosphere by waves breaking on sea surfaces provide an important contribution
to the planetary albedo. During the International Chemistry Experiment in the Arctic
LOwer ...
Cirrus clouds are ubiquitous in the tropical tropopause region and play a major role
in the Earth’s climate. Any changes to cirrus abundance due to natural or anthropogenic
influences must be considered to evaluate future climate change. The detailed ...
This study focuses on the retrieval of the normalized mass absorption cross section
(MAC) of soot using theoretical calculations that incorporate new measurements of
the optical properties of organic carbon (OC) intrinsic to fresh diesel soot. Intrinsic
...
Mathematics
We introduce some combinatorial objects called staircase tableaux, which have cardinality
4nn !, and connect them to both the asymmetric exclusion process (ASEP) and Askey-Wilson
polynomials. The ASEP is a model from statistical mechanics introduced in ...
Physics
The human red blood cell (RBC) membrane, a fluid lipid bilayer tethered to an elastic
2D spectrin network, provides the principal control of the cell’s morphology and mechanics.
These properties, in turn, influence the ability of RBCs to transport oxygen ...
Statistics
To many biomedical researchers, effective tumor classification methods such as the
support vector machine often appear like a black box not only because the procedures
are complex but also because the required specifications, such as the choice of a
...
Respondent-driven sampling (RDS) is a network-based technique for estimating traits
in hard-to-reach populations, for example, the prevalence of HIV among drug injectors.
In recent years RDS has been used in more than 120 studies in more than 20 countries
...
Social Sciences
Environmental Sciences
The “hydraulic city” of Angkor, the capitol of the Khmer Empire in Cambodia, experienced
decades-long drought interspersed with intense monsoons in the fourteenth and fifteenth
centuries that, in combination with other factors, contributed to its eventual ...
Psychological and Cognitive Sciences
When we judge an action as morally right or wrong, we rely on our capacity to infer
the actor's mental states (e.g., beliefs, intentions). Here, we test the hypothesis
that the right temporoparietal junction (RTPJ), an area involved in mental state ...
Hemodynamic measures of brain activity can be used to interpret a student's mental
state when they are interacting with an intelligent tutoring system. Functional magnetic
resonance imaging (fMRI) data were collected while students worked with a tutoring
...
Biological Sciences
Anthropology
The Farming/Language Dispersal Hypothesis posits that prehistoric population expansions,
precipitated by the innovation or early adop-tion of agriculture, played an important
role in the uneven distribution of language families recorded across the world. ...
Applied Biological Sciences
The human red blood cell (RBC) membrane, a fluid lipid bilayer tethered to an elastic
2D spectrin network, provides the principal control of the cell’s morphology and mechanics.
These properties, in turn, influence the ability of RBCs to transport oxygen ...
Biochemistry
Mediator recently has emerged as a central player in the direct transduction of signals
from transcription factors to the general transcriptional machinery. In the case of
nuclear receptors, in vitro studies have shown that the transcriptional coactivator
...
The C-terminal segment of the human insulin receptor α-chain (designated αCT) is critical
to insulin binding as has been previously demonstrated by alanine scanning mutagenesis
and photo-cross-linking. To date no information regarding the structure of ...
Many archaea (including all the methanogens, nearly all euryarchaeotes, and some crenarchaeotes)
use histones as components of the chromatin that compacts their genomes. The archaeal
histones are homo- and heterodimers that pair on DNA to form tetrasomes (...
The ring-shaped helicase of bacteriophage T7 (gp4), the product of gene 4, has basic
β-hairpin loops lining its central core where they are postulated to be the major
sites of DNA interaction. We have altered multiple residues within the β-hairpin loop
to ...
The polycomb repressive complex (PRC) 1 protein Ring1B is an ubiquitin ligase that
modifies nucleosomal histone H2A, a modification which plays a critical role in regulation
of gene expression. We have shown that self-ubiquitination of Ring1B generates ...
The key to understanding amyloid disease is the characterization of oligomeric species
formed during the early stages of fibril assembly. Here we have used electrospray
ionisation-ion mobility spectrometry-mass spectrometry to identify and structurally
...
The powerstroke of the myosin motor is the basis of cell division and bodily movement,
but has eluded empirical description due to the short lifetime and low abundance of
intermediates during force generation. To gain insight into this process, we used
...
Formation of a complex between the XRCC1 N-terminal domain (NTD) and DNA polymerase
β (Pol β) is central to base excision repair of damaged DNA. Two crystal forms of
XRCC1-NTD complexed with Pol β have been solved, revealing that the XRCC1-NTD is able
to ...
PorB is the second most prevalent outer membrane protein in Neisseria meningitidis. PorB is required for neisserial pathogenesis and can elicit a Toll-like receptor
mediated host immune response. Here, the x-ray crystal structure of PorB has been
...
The joint x-ray/neutron diffraction model of the Type I copper protein, amicyanin
from Paracoccus denitrificans was determined at 1.8 Å resolution. The protein was crystallized using reagents prepared
in D2O. About 86% of the amide hydrogen atoms are ...
Biophysics and Computational Biology
To many biomedical researchers, effective tumor classification methods such as the
support vector machine often appear like a black box not only because the procedures
are complex but also because the required specifications, such as the choice of a
...
The rapid accumulation of gene expression data has offered unprecedented opportunities
to study human diseases. The National Center for Biotechnology Information Gene Expression
Omnibus is currently the largest database that systematically documents the ...
We describe an optical method capable of tracking a single fluorescent molecule with
a flexible choice of high spatial accuracy (∼10–20 nm standard deviation or ∼20–40 nm
full-width-at-half-maximum) and temporal resolution (< 1 ms). The fluorescence ...
Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) has been implicated in Parkinson’s
disease (PD) and is present in neurofibrillary tangles or Lewy bodies. However, the
molecular basis for UCH-L1s involvement in proteinacious fibril formation is still
...
Gene regulatory networks have been shown to share some common aspects with commonplace
social governance structures. Thus, we can get some intuition into their organization
by arranging them into well-known hierarchical layouts. These hierarchies, in turn,...
Repair of damage to the central nervous system (CNS) is inhibited by the presence
of myelin proteins that prevent axonal regrowth. Consequently, growth inhibitors and
their common receptor have been identified as targets in the treatment of injury to
the ...
Siphoviridae is the most abundant viral family on earth which infects bacteria as well as archaea.
All known siphophages infecting gram+ Lactococcus lactis possess a baseplate at the tip of their tail involved in host recognition and attachment.
Here, we ...
Cell Biology
An important aspect of vascular biology is the identification of regulators of stress-sensitive
genes that play critical roles in mediating inflammatory response. Here, we show that
expression of HuR in human umbilical vein endothelial cells is regulated ...
The Drosophila Dachshund (Dac) gene, cloned as a dominant inhibitor of the hyperactive growth factor mutant ellipse, encodes a key component of the retinal determination gene network that governs cell
fate. Herein, cyclic amplification and selection of ...
UV irradiation induces histone variant H2AX phosphorylated on serine 139 (γH2AX) foci
and high levels of pan-nuclear γH2AX staining without foci, but the significance of
this finding is still uncertain. We examined the formation of γH2AX and 53BP1 that
...
Cortical endoplasmic reticulum (cER) is a permanent feature of yeast cells but occurs
transiently in most animal cell types. Ist2p is a transmembrane protein that permanently
localizes to the cER in yeast. When Ist2 is expressed in mammalian cells, it ...
Survival of differentiated cells is one of several processes regulated by Notch activity,
although the general principles underlying this function remain to be characterized.
Here, we probe the mechanism underlying Notch-mediated survival, building on ...
Aneuploidy is a characteristic feature of established cancers and can promote tumor
development. Aneuploidy may arise directly, through unequal distribution of chromosomes
into daughter cells, or indirectly, through a tetraploid intermediate. The polo ...
Plants exhibit an ultimate case of the intracellular motility involving rapid organelle
trafficking and continuous streaming of the endoplasmic reticulum (ER). Although it
was long assumed that the ER dynamics is actomyosin-driven, the responsible myosins
...
The Wnt pathway regulates multiple biological and pathological processes including
angiogenesis and inflammation. Here we identified a unique inhibitor of the Wnt pathway,
SERPINA3K, a serine proteinase inhibitor with anti-inflammatory and angiogenic ...
The Wnt/planar cell polarity (PCP) pathway regulates directed cell movement during
development and was recently found to play a critical role in endothelial cell proliferation
and angiogenesis [Zhang Y, et al. (2006) Chem Biol 13:1001–1009; Masckauchan TN,...
Glioblastoma multiforme (GBM) is the most common and lethal primary brain cancer that
is driven by aberrant signaling of growth factor receptors, particularly the epidermal
growth factor receptor (EGFR). EGFR signaling is tightly regulated by receptor ...
MyTH/FERM (myosin tail homology 4/band 4.1, ezrin, radixin, and moesin) myosins have
roles in cellular adhesion, extension of actin-filled projections such as filopodia
and stereocilia, and directional migration. The amoeba Dictyostelium discoideum ...
Developmental Biology
Despite substantial size variations, proportions of the developing body plan are maintained
with a remarkable precision. Little is known about the mechanisms that ensure this
adaptation (scaling) of pattern with size. Most models of patterning by ...
Different signaling pathways are deployed in specific developmental contexts to generate
sexually dimorphic traits. Recently, Sex-lethal (Sxl), the female determinant in Drosophila melanogaster, was shown to down-regulate Notch (N) signaling to accomplish ...
Ecology
Although populations of amphibians are declining worldwide, there is no evidence that
salamanders occupying small streams are experiencing enigmatic declines, and populations
of these species seem stable. Theory predicts that dispersal through multiple ...
Recent evidence suggests that bats can detect the geomagnetic field, but the way in
which this is used by them for navigation to a home roost remains unresolved. The
geomagnetic field may be used by animals both to indicate direction and to locate
...
Evolution
A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon
isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused
by eruptions of continental flood basalt provinces. However, the necessary serial
...
View related content:
Mass extinctions of life and catastrophic flood basalt volcanism
Genetics
Oscillations in patterns of expression of a large fraction of yeast genes are associated
with the “metabolic cycle,” usually seen only in prestarved, continuous cultures of
yeast. We used FISH of mRNA in individual cells to test the hypothesis that these
...
Global loss of DNA methylation has been known for decades as an epigenomic aberration
associated with carcinogenesis and cancer progression. Loss of DNA methylation affects
predominantly repetitive elements, which encompass >50% of the CpG dinucleotides ...
Immunology
Abs are central to malaria immunity, which is only acquired after years of exposure
to Plasmodium falciparum (Pf). Despite the enormous worldwide burden of malaria, the targets of protective Abs
and the basis of their inefficient acquisition are unknown. ...
MHC class I molecules function to display peptides generated from cellular and pathogen
gene products for immune surveillance by CD8+ T cells. Cells typically express ∼100,000 class I molecules, or ∼1 per 30,000 cellular
proteins. Given “one protein, one ...
The envelope glycoprotein of vesicular stomatitis virus (VSV-G) enables viral entry
into hosts as distant as insects and vertebrates. Because of its ability to support
infection of most, if not all, human cell types VSV-G is used in viral vectors for
gene ...
Medical Sciences
Ischemia complicates wound closure. Here, we are unique in presenting a murine ischemic
wound model that is based on bipedicle flap approach. Using this model of ischemic
wounds we have sought to elucidate how microRNAs may be implicated in limiting wound
...
Inactivation of mismatch repair (MMR) is the cause of the common cancer predisposition
disorder Lynch syndrome (LS), also known as hereditary nonpolyposis colorectal cancer
(HNPCC), as well as 10–40% of sporadic colorectal, endometrial, ovarian, gastric,
...
Pantothenate kinase–associated neurodegeneration (PKAN), a progressive neurodegenerative
disorder, is associated with impairment of pantothenate kinase function. Pantothenate
kinase is the first enzyme required for de novo synthesis of CoA, an essential ...
The hallmark of human cancer is heterogeneity, reflecting the complexity and variability
of the vast array of somatic mutations acquired during oncogenesis. An ability to
dissect this heterogeneity, to identify subgroups that represent common mechanisms
...
Pathologic hypertrophy of the heart is regulated through membrane-bound receptors
and intracellular signaling pathways that function, in part, by altering Ca2+ handling and Ca2+-dependent signaling effectors. Transient receptor potential canonical (TRPC) ...
Microbiology
The AcrB trimeric multidrug efflux transporter of Escherichia coli pumps out a very wide spectrum of compounds. Although minocycline and doxorubicin
have been cocrystallized within the large binding pocket in the periplasmic domain
of the binding protomer,...
Certain types of human papillomaviruses (HPVs) are etiologically linked to cervical
cancer. Their transforming capacity is encoded by a polycistronic premRNA, where alternative
splicing leads to the translation of functional distinct proteins such as E6, ...
Caulobacter crescentus integrates phospho-signaling pathways and transcription factor regulatory cascades
to drive the cell cycle. Despite the essential role of the CckA histidine kinase in
the control of cell cycle events, the factors that signal its ...
Neuroscience
Hemodynamic measures of brain activity can be used to interpret a student's mental
state when they are interacting with an intelligent tutoring system. Functional magnetic
resonance imaging (fMRI) data were collected while students worked with a tutoring
...
The autonomic nervous system regulates fuel availability and energy storage in the
liver, adipose tissue, and other organs; however, the molecular components of this
neural circuit are poorly understood. We sought to identify neural populations that
...
Learning-induced trophic activity is thought to be critical for maintaining health
of the aging brain. We report here that learning, acting through an unexpected pathway,
activates synaptic receptors for one of the brain's primary trophic factors. ...
Recent epidemiological studies suggest that diabetes mellitus is a strong risk factor
for Alzheimer disease. However, the underlying mechanisms remain largely unknown.
In this study, to investigate the pathophysiological interaction between these diseases,...
View related content:
Mutations of leukemia-associated AF9/MLLT3 are implicated in neurodevelopmental diseases, such as epilepsy and ataxia, but little
is known about how AF9 influences brain development and function. Analyses of mouse
mutants revealed that during cortical ...
Sonar broadcasts are followed by echoes at different delays from objects at different
distances. When broadcasts are emitted rapidly in cluttered surroundings, echo streams
from successive broadcasts overlap and cause ambiguity in matching echoes to ...
Episodic memory requires the hippocampus, which is thought to bind cortical inputs
into conjunctive codes. Local field potentials (LFPs) reflect dendritic and synaptic
oscillations whose temporal structure may coordinate cellular mechanisms of plasticity
...
Multiple intracellular signals are altered in Alzheimer's disease brain tissues, including
the PI3K/Akt pathway. However, the pathological relevance of such alterations is poorly
understood. In vitro studies yield results that seem to be consistent with ...
Pharmacology
G-protein heterotrimers, composed of a guanine nucleotide-binding Gα subunit and an
obligate Gβγ dimer, regulate signal transduction pathways by cycling between GDP-
and GTP-bound states. Signal deactivation is achieved by Gα-mediated GTP hydrolysis
(...
Physiology
Hypertonicity activates the transcription factor TonEBP/OREBP, resulting in increased
expression of osmoprotective genes, including those responsible for accumulation of
organic osmolytes and heat-shock proteins. Phosphorylation of TonEBP/OREBP ...
The structure and motion of elephant limbs are unusual compared with those of other
animals. Elephants stand and move with straighter limbs (at least when walking), and
have limited speed and gait. We devised novel experiments to examine how the limbs
of ...
Temperature sensing is crucial for homeotherms, including human beings, to maintain
a stable body core temperature and respond to the ambient environment. A group of
exquisitely temperature-sensitive transient receptor potential channels, termed ...
Plant Biology
Plant high-affinity K+ transport (HKT) proteins are so named because of their relation to bacterial and fungal
transporters that mediate high-affinity K+ uptake. The view that HKT family members are sodium-selective uniporters or sodium-potassium
...
Karrikins are a class of seed germination stimulants identified in smoke from wildfires.
Microarray analysis of imbibed Arabidopsis thaliana seeds was performed to identify transcriptional responses to KAR1 before germination. A small set of genes that ...
To address complications of pathogenic antibody or life-threatening anaphylactic reactions
in protein replacement therapy for patients with hemophilia or other inherited protein
deficiencies, we have developed a prophylactic protocol using a murine ...
Systems Biology
Ligand-mediated gene induction by steroid receptors is a multistep process characterized
by a dose–response curve for gene product that follows a first-order Hill equation.
This behavior has classically been explained by steroid binding to receptor being
...
Corrections
Cover image: Pictured are frost flowers on Arctic sea ice. Frost flowers may release significant quantities of molecular bromine into the springtime polar atmosphere. This halogen compound forms bromine oxide, which destroys ozone. Denis Pöhler et al. measured high bromine oxide concentrations in the lower Arctic atmosphere above sea ice, suggesting that naturally occurring halogens may play a more integral role in ozone depletion than previously thought. See the article by Pöhler et al. on pages 6582–6587, which is part of the Atmospheric Chemistry Special Feature. Photograph courtesy of Denis Pöhler.
Advertisement
Recent Issues
Submit to PNAS
Submit to the Proceedings of the National Academy of Sciences (PNAS) and have your research discovered by millions of researchers in the Biological, Physical, and Social Sciences.
Submit your manuscript