787 research outputs found
Elementary Functional Properties of Single HCN2 Channels
AbstractHyperpolarization-activated cyclic-nucleotide-gated (HCN) channels are tetramers that evoke rhythmic electrical activity in specialized neurons and cardiac cells. These channels are activated by hyperpolarizing voltage, and the second messenger cAMP can further enhance the activation. Despite the physiological importance of HCN channels, their elementary functional properties are still unclear. In this study, we expressed homotetrameric HCN2 channels in Xenopus oocytes and performed single-channel experiments in patches containing either one or multiple channels. We show that the single-channel conductance is as low as 1.67 pS and that channel activation is a one-step process. We also observed that the time between the hyperpolarizing stimulus and the first channel opening, the first latency, determines the activation process alone. Notably, at maximum hyperpolarization, saturating cAMP drives the channel to open for unusually long periods. In particular, at maximum activation by hyperpolarization and saturating cAMP, the open probability approaches unity. In contrast to other reports, no evidence of interchannel cooperativity was observed. In conclusion, single HCN2 channels operate only with an exceptionally low conductance, and both activating stimuli, voltage and cAMP, exclusively control the open probability
Single grain heating due to inelastic cotunneling
We study heating effects of a single metallic quantum dot weakly coupled to
two leads. The dominant mechanism for heating at low temperatures is due to
inelastic electron cotunneling processes. We calculate the grain temperature
profile as a function of grain parameters, bias voltage, and time and show that
for nanoscale size grains the heating effects are pronounced and easily
measurable in experiments.Comment: 4 pages, 3 figures, revtex4, extended and corrected versio
Deterministic nano-assembly of a coupled quantum emitter - photonic crystal cavity system
The interaction of a single quantum emitter with its environment is a central
theme in quantum optics. When placed in highly confined optical fields, such as
those created in optical cavities or plasmonic structures, the optical
properties of the emitter can change drastically. In particular, photonic
crystal (PC) cavities show high quality factors combined with an extremely
small mode volume. Efficiently coupling a single quantum emitter to a PC cavity
is challenging because of the required positioning accuracy. Here, we
demonstrate deterministic coupling of single Nitrogen-Vacancy (NV) centers to
high-quality gallium phosphide PC cavities, by deterministically positioning
their 50 nm-sized host nanocrystals into the cavity mode maximum with
few-nanometer accuracy. The coupling results in a 25-fold enhancement of NV
center emission at the cavity wavelength. With this technique, the NV center
photoluminescence spectrum can be reshaped allowing for efficient generation of
coherent photons, providing new opportunities for quantum science.Comment: 13 pages, 4 figure
The Slowly Formed Guiselin Brush
We study polymer layers formed by irreversible adsorption from a polymer
melt. Our theory describes an experiment which is a ``slow'' version of that
proposed by Guiselin [Europhys. Lett., v. 17 (1992) p. 225] who considered
instantaneously irreversibly adsorbing chains and predicted a universal density
profile of the layer after swelling with solvent to produce the ``Guiselin
brush.'' Here we ask what happens when adsorption is not instantaneous. The
classic example is chemisorption. In this case the brush is formed slowly and
the final structure depends on the experiment's duration, . We find
the swollen layer consists of an inner region of thickness with approximately constant density and an outer region
extending up to height which has the same density decay as for the Guiselin case.Comment: 7 pages, submitted to Europhysics Letter
Identification and Comparison of Colletotrichum Secreted Effector Candidates Reveal Two Independent Lineages Pathogenic to Soybean
Colletotrichum is one of the most important plant pathogenic genus of fungi due to its scientific and economic impact. A wide range of hosts can be infected by Colletotrichum spp., which causes losses in crops of major importance worldwide, such as soybean. Soybean anthracnose is mainly caused by C. truncatum, but other species have been identified at an increasing rate during the last decade, becoming one of the most important limiting factors to soybean production in several regions. To gain a better understanding of the evolutionary origin of soybean anthracnose, we compared the repertoire of effector candidates of four Colletotrichum species pathogenic to soybean and eight species not pathogenic. Our results show that the four species infecting soybean belong to two lineages and do not share any effector candidates. These results strongly suggest that two Colletotrichum lineages have acquired the capability to infect soybean independently. This study also provides, for each lineage, a set of candidate effectors encoding genes that may have important roles in pathogenicity towards soybean offering a new resource useful for further research on soybean anthracnose management
Studies of inactivation mechanism of non-enveloped icosahedral virus by a visible ultrashort pulsed laser
BACKGROUND: Low-power ultrashort pulsed (USP) lasers operating at wavelengths of 425 nm and near infrared region have been shown to effectively inactivate viruses such as human immunodeficiency virus (HIV), M13 bacteriophage, and murine cytomegalovirus (MCMV). It was shown previously that non-enveloped, helical viruses such as M13 bacteriophage, were inactivated by a USP laser through an impulsive stimulated Raman scattering (ISRS) process. Recently, enveloped virus like MCMV has been shown to be inactivated by a USP laser via protein aggregation induced by an ISRS process. However, the inactivation mechanism for a clinically important class of viruses – non-enveloped, icosahedral viruses remains unknown. RESULTS AND DISCUSSIONS: We have ruled out the following four possible inactivation mechanisms for non-enveloped, icosahedral viruses, namely, (1) inactivation due to ultraviolet C (UVC) photons produced by non-linear optical process of the intense, fundamental laser beam at 425 nm; (2) inactivation caused by thermal heating generated by the direct laser absorption/heating of the virion; (3) inactivation resulting from a one-photon absorption process via chromophores such as porphyrin molecules, or indicator dyes, potentially producing reactive oxygen or other species; (4) inactivation by the USP lasers in which the extremely intense laser pulse produces shock wave-like vibrations upon impact with the viral particle. We present data which support that the inactivation mechanism for non-enveloped, icosahedral viruses is the impulsive stimulated Raman scattering process. Real-time PCR experiments show that, within the amplicon size of 273 bp tested, there is no damage on the genome of MNV-1 caused by the USP laser irradiation. CONCLUSION: We conclude that our model non-enveloped virus, MNV-1, is inactivated by the ISRS process. These studies provide fundamental knowledge on photon-virus interactions on femtosecond time scales. From the analysis of the transmission electron microscope (TEM) images of viral particles before and after USP laser irradiation, the locations of weak structural links on the capsid of MNV-1 were revealed. This important information will greatly aid our understanding of the structure of non-enveloped, icosahedral viruses. We envision that this non-invasive, efficient viral eradication method will find applications in the disinfection of pharmaceuticals, biologicals and blood products in the near future
Comparative Transcriptomic Provides Novel Insights into the Soybean Response to Colletotrichum truncatum infection
Soybean (Glycine max) is among the most important crops in the world and its production can be threatened by biotic diseases, such as anthracnose. Soybean anthracnose is a seed-borne disease mainly caused by the hemibiotrophic fungus Colletotrichum truncatum. Typical symptoms are pre- and post-emergence damping-off, necrotic lesions on cotyledons, petioles, leaves, and pods. Anthracnose symptoms can appear early in the field, causing major losses to soybean production. In preliminary experiments, we observed that the same soybean cultivar can have a range of susceptibility towards different strains of C. truncatum, while the same C. truncatum strain can cause varying levels of disease severity in different soybean cultivars. To gain a better understanding of the molecular mechanisms regulating the early response of different soybean cultivars to different C. truncatum strains, we performed pathogenicity assays to select two soybean cultivars with significantly different susceptibility to two different C. truncatum strains and analyzed their transcriptome profiles at different time-points of interaction (0, 12, 48, and 120 hours post-inoculation - hpi). The pathogenicity assays showed that the soybean cultivar Gm1 is more resistant to C. truncatum strain 1080, and it is highly susceptible to strain 1059, while cultivar Gm2 shows the opposite behavior. However, if only trivial anthracnose symptoms appeared in the More Resistant Phenotype (MRP; Gm1-1080; Gm2-1059) upon 120 hpi, in the More Susceptible Phenotype (MSP; Gm-1059; Gm2- 1080) plants show mild symptoms already at 72 hpi, after which disease evolved rapidly to severe necrosis and plant death. Interestingly, several genes related to different cellular responses of the plant immune system (pathogen recognition, signaling events, transcriptional reprogramming, and defense-related genes) were commonly modulated at the same time-points only in both MRP. The list of differentially expressed genes (DEGs) specific to the more resistant combinations and related to different cellular responses of the plant immune system may shed light on the important host defense pathways against soybean anthracnose
Complete Genome Sequence of the Plant-Pathogenic Fungus Colletotrichum lupini
Colletotrichum is a fungal genus (Ascomycota, Sordariomycetes, Glomerellaceae) that includes many economically important plant pathogens that cause devastating diseases of a wide range of plants. In this work, using a combination of long- and short-read sequencing technologies, we sequenced the genome of Colletotrichum lupini RB221, isolated from white lupin (Lupinus albus) in France during a survey in 2014. The genome was assembled into 11 nuclear chromosomes and a mitochondrial genome with a total assembly size of 63.41 Mb and 36.55 kb, respectively. In total, 18,324 protein-encoding genes have been predicted, of which only 39 are specific to C. lupini. This resource will provide insight into pathogenicity factors and will help provide a better understanding of the evolution and genome structure of this important plant pathogen
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