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1.
Different odorants are recognized by different combinations of G protein-coupled olfactory receptors, and thereby, odor identity is determined by a combinatorial receptor code for each odorant. We recently demonstrated that odorants appeared to compete for receptor sites to act as an agonist or an antagonist. Therefore, in natural circumstances where we always perceive a mixture of various odorants, olfactory receptor antagonism between odorants may result in a receptor code for the mixture that cannot be predicted from the codes for its individual components. Here we show that stored isoeugenol has an antagonistic effect on a mouse olfactory receptor, mOR-EG. However, freshly purified isoeugenol did not have an inhibitory effect. Instead, an isoeugenol derivative produced during storage turned out to be a potent competitive antagonist of mOR-EG. Structural analysis revealed that this derivative is an oxidatively dimerized isoeugenol that naturally occurs by oxidative reaction. The current study indicates that as odorants age, they decompose or react with other odorants, which in turn affects responsiveness of an olfactory receptor(s). 相似文献
2.
V. A. Fedorov 《Plasma Physics Reports》2010,36(7):636-642
Dynamics of an electron layer incident on the surface of an electrically insulated conducting body with an unsteady self-consistent positive charge is investigated. At the initial instant, the electron velocity is directed toward the body and the electron layer is not adjacent to the body surface. One-dimensional plane, cylindrical, and spherical electron motions in vacuum and against the background of motionless ions and neutral particles are considered. Exact analytical solutions to the set of nonlinear plasma hydrodynamics equations with absorbing boundary conditions for electrons are obtained. The spatial and time dependences of the electric field, electron density, and electron velocity are found. The time evolution of the surface charge density is determined. 相似文献
3.
Hans H. Pfeiffer 《Protoplasma》1941,36(1):444-449
Zusammenfassung In Ergänzung zu polarisationsmikroskopischen Untersuchungen isotonisch und isometrisch kontrahierter Insektenmuskeln sind beugungspolarisatorische Messungen an jenen und an einem Muskelmodell (Myosinfäden) angestellt worden. Soweit die Befunde heute schon gedeutet werden können, sind sie als Bestätigung des polarisations- und röntgenoptisch, visko- und thermoelastisch und nach dem kolloiden Verhalten erschlossenen leptonischen Bauplans der Objekte anzusehen. 相似文献
4.
Fatal attack on an infant by an adult female tonkean macaque 总被引:1,自引:0,他引:1
We describe a fatal attack on a 10-month-old female infant by an adult female Tonkean macaque (Macaca tonkeana)in a semi-free-ranging group. During an intense conflict involving many group members, an adult female, the second most dominant
in the group, attacked the infant of a lower-ranking female. The attacker remained near the victim for approximately 20 min,
grabbing and biting it repeatedly, until the mother retrieved the infant. She died 2 days later. An autopsy revealed no lethal
injury;the main cause of death was starvation or dehydration or both. We discuss social conditions under which a fatal attack by
an adult female might occur. 相似文献
5.
《Anthrozo?s》2013,26(4):259-264
AbstractProper diagnostic assessment in an inpatient psychiatric setting requires observation of patients under various conditions. Group activities such as animal-assisted therapy (A-AT) can provide an excellent opportunity for assessment—but only if the patient chooses to attend. Retrospective analysis of attendance at a major metropolitan inpatient psychiatric unit indicates that over the course of two years (N= 23 months) the A-AT group attracted the highest percentage of inpatients voluntarily choosing to attend an occupational therapy group. It was found that A-AT was the most effective of all groups offered in attracting isolated individuals regardless of diagnosis. The authors conclude that A-AT is an effective tool for diagnostic observation and assessment. 相似文献
6.
Rinaldo Schinazi 《Journal of mathematical biology》1996,34(8):915-925
We consider an interacting particle system onZ
dto model an epidemic. Each site ofZ
dcan be in either one of three states: empty, healthy or infected. Healthy and infected individuals give birth at different rates to healthy individuals on empty sites. Healthy individuals get infected by infected individuals. Infected and healthy individuals die at different rates. We prove that in dimension 1 and with nearest-neighbor interactions the epidemic may persist forever if and only if the rate at which infected individuals give birth to healthy individuals is high enough. This is in sharp contrast with models analysed by Andjel and Schinazi (1994) and Sato et al. (1994) where infected individuals do not give birth. We also show that some results in the latter reference can be obtained easily and rigorously using probabilistic coupling to the contact process. 相似文献
7.
The electric charges on an enzyme may move concomitantly with a conformational change. Such an enzyme will absorb energy from an oscillating electric field. If in addition the enzyme has a larger association constant for substrate than for product, as is often true, it can use this energy to drive the catalyzed reaction away from equilibrium. Approximate analytical expressions are given for the field-driven flux, electrical power absorbed, free-energy produced per unit time, thermodynamic efficiency, and zero-flux concentrations. The field-driven flux is written as a generalized Michaelis-Menten equation. 相似文献
8.
S ummary . An organism causing an off-flavour in an orange juice drink is described. Morphological and biochemical properties of this organism, which produces a characteristic coral pink growth on most media, are also reported. Possible relationships with similar organisms known to occur in fruit juices and on fruits are discussed. 相似文献
9.
Zhu X Larsen NA Basran A Bruce NC Wilson IA 《The Journal of biological chemistry》2003,278(3):2008-2014
The crystal structures of an acetyl esterase, HerE, and its complex with an inhibitor dimethylarsinic acid have been determined at 1.30- and 1.45-A resolution, respectively. Although the natural substrate for the enzyme is unknown, HerE hydrolyzes the acetyl groups from heroin to yield morphine and from phenyl acetate to yield phenol. Recently, the activity of the enzyme toward heroin has been exploited to develop a heroin biosensor, which affords higher sensitivity than other currently available detection methods. The crystal structure reveals a single domain with the canonical alpha/beta hydrolase fold with an acyl binding pocket that snugly accommodates the acetyl substituent of the substrate and three backbone amides that form a tripartite oxyanion hole. In addition, a covalent adduct was observed between the active site serine and dimethylarsinic acid, which inhibits the enzyme. This crystal structure provides the first example of an As-containing compound in a serine esterase active site and the first example of covalent modification of serine by arsenic. Thus, the HerE complex reveals the structural basis for the broad scope inhibition of serine hydrolases by As(V)-containing organic compounds. 相似文献
10.
To illustrate the usefulness of mathematical models to the microbiology and medical communities, we explain how to construct and apply a simple transmission model of an emerging pathogen. We chose to model, as a case study, a large (>8,000 reported cases) on-going outbreak of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) in the Los Angeles County Jail. A major risk factor for CA-MRSA infection is incarceration. Here, we show how to design a within-jail transmission model of CA-MRSA, parameterize the model and reconstruct the outbreak. The model is then used to assess the severity of the outbreak, predict the epidemiological consequences of a catastrophic outbreak and design effective interventions for outbreak control. 相似文献
11.
A 40 amino acid sequence of the unsolved structure of Escherichia coli alanine-tRNA synthetase is essential for tRNA binding and encodes an immunological determinant that cross-reacts with antibodies raised against a eukaryote (insect Bombyx mori) alanine enzyme. The secondary structure of this sequence is predicted to be an amphiphilic alpha-helix that includes one aspartyl and eight glutamyl side chain carboxyl groups. The antibody reactivity and the conformation of a synthetic peptide model of this region (Glu346 to Ser385) were investigated. In addition, double Arg----Gln and Leu----Ala substitutions were separately placed in the enzyme on the hydrophilic and hydrophobic face, respectively, of the predicted helix. These mutations conserve the polar/nonpolar character of each face and retain the potential for helix formation. Circular dichroism spectra of the synthetic peptide model demonstrate the potential for amphiphilic helix formation for the segment from Glu346 to Ser385. The behavior of the mutations in the enzyme, together with earlier data and immunological assays presented here, suggests that one face of the putative helix is an antigenic region of the surface of the enzyme where it contributes to the interaction with alanine tRNA and that the specific sequence of the helix is an important determinant of enzyme stability. 相似文献
12.
We recently reported a deep learning model to facilitate fragment library design, which is critical for efficient hit identification. However, our model was implemented in Python. We have now created an implementation in the KNIME graphical pipelining environment which we hope will allow experimentation by users with limited programming knowledge.We report a deep learning model to facilitate fragment library design, which is critical for efficient hit identification, and an implementation in the KNIME graphical workflow environment which should facilitate a more codeless use. 相似文献
13.
We develop approximate methods to compare the efficiencies and to compute the power of alternative potential designs for sampling from a cohort before beginning to collect exposure data. Our methods require only that the cohort be assembled, meaning that the numbers of individuals Nkj at risk at pairs of event times tk and tj greater than or equal to tk are available. To compute Nkj, one needs to know the entry, follow-up, censoring, and event history, but not the exposure, for each individual. Our methods apply to any "unbiased control sampling design," in which cases are compared to a random sample of noncases at risk at the time of an event. We apply our methods to approximate the efficiencies of the nested case-control design, the case-cohort design, and an augmented case-cohort design, compared to the full cohort design, in an assembled cohort of 17,633 members of an insurance cooperative who were followed for mortality from prostatic cancer. The assumptions underlying the approximation are that exposure is unrelated both to the hazard of an event and to the hazard for censoring. The approximations performed well in simulations when both assumptions held and when the exposure was moderately related to censoring. 相似文献
14.
The distribution of the solid-phase in an airlift reactor of the concentric draught tube type, with an enlarged degassing zone, has been determined. Samples were taken at eight points of the reactor for various airflow rates, solids loading and density. Hold-up of solids varied considerably within the reactor. The highest value, for all tested experimental conditions, was obtained immediately above the top of the riser and the lowest value near the wall of the degassing zone. © Rapid Science Ltd, 1998 相似文献
15.
An exactly solvable model is used as a basis to study the reflectionless passage of a transverse electromagnetic wave through
an inhomogeneous plasma containing large-amplitude, small-scale (subwave-length) structures (in particular, opaque regions)
that cannot be correctly described by approximate methods. It is shown that, during the reflectionless passage of an electromagnetic
wave, strong wave field splashes can occur in certain plasma sublayers. The nonuniform spatial plasma density profile is characterized
by a number of free parameters describing the modulation depth of the dielectric function, the characteristic sizes of the
structures and their number, the thickness of the inhomogeneous plasma region, and so on. Such plasma density structures are
shown to be very diverse when, e.g., a wave that is incident from vacuum propagates without reflection through a plasma layer
(wave barrier transillumination). With the cubic nonlinearity taken into account, a one-dimensional problem of the nonlinear
transillumination of an inhomogeneous plasma can be solved exactly. 相似文献
16.
Exotic pathogen invasions can change host eco-evolutionary interactions and possibly create an evolutionary trap when the pathogen generates mismatches between developmental phenology and reproductive cues. Taylor’s checkerspot butterfly (Euphydryas editha taylori), is an endangered species of western North America with 80 % of the extant populations dependent on an exotic host, Plantago lanceolata. Survey of occupied, recently extinct, and unsuccessful butterfly reintroduction sites spanning 4° of latitude revealed widespread disease on P. lanceolata caused by Pyrenopeziza plantaginis. This fungal pathogen, new to North America, reduces the standing crop of P. lanceolata foliage throughout the winter post-diapause larval feeding period. However, disease is absent when adult butterflies and pre-diapause larvae are active. Diseased plants were frequent in Taylor’s checkerspot populations with a history of persistence, but >90 % of the host plants in these populations had initiated new leaves within the first few weeks of post-diapause larval feeding. Conversely, host plants in recently extinct and unsuccessfully reintroduced populations were severely diseased, >66 % mean foliage necrosis/plant, and <23 % had initiated new leaves. Feeding choice trials with 25 larvae indicated that new leaves were strongly and consistently preferred by post-diapause larvae over all other available leaf types, both diseased and non-diseased. Because the influence of disease on post-diapause larval food resources is developmentally disassociated from oviposition, P. plantaginis invasion appears to have triggered an evolutionary trap for Plantago-dependent populations of Taylor’s checkerspot. 相似文献
17.
S. V. Kochetkova E. A. Fillipova N. A. Kolganova E. N. Timofeev V. L. Florentiev 《Russian Journal of Bioorganic Chemistry》2008,34(2):207-214
Oligonucleotide analogues bearing an acyclocytidine linked to thymidine with an amide (3′-O-CH2-CO-N-5′) bond were synthesized. Melting curves of duplexes formed by modified oligonucleotides and complementary natural oligomers were obtained and thermodynamic parameters of their formation were measured. Replacement of dCpT by a modified dinucleotide only moderately decreased the melting temperature of these modified duplexes in comparison with unmodified duplexes containing complementary natural bases. CD spectra of modified duplexes were studied, and the duplex spatial structures are discussed. 相似文献
18.
Phloretin - an uncoupler and an inhibitor of mitochondrial oxidative phosphorylation 总被引:2,自引:0,他引:2
P C De Jonge T Wieringa J P Van Putten H M Krans K Van Dam 《Biochimica et biophysica acta》1983,722(1):219-225
The effect of phloretin on respiration by isolated mitochondria and submitochondrial particles was studied. In submitochondrial particles, both NADH- and succinate-dependent respiration was inhibited by phloretin. 50% maximum inhibition was reached at phloretin concentrations of 0.1 mM (NADH oxidation) and 0.7 mM (succinate oxidation). In isolated mitochondria, phloretin inhibited glutamate oxidation in both State 3 and State 4; 50% maximum inhibition occurred at about 30 microM. Succinate oxidation is inhibited in State 3 by phloretin, inhibition being half its maximum value at 0.5 mM, but in State 4 it is stimulated about 2-fold by phloretin at a concentration of 0.6 mM. Ascorbate oxidation is stimulated in both State 3 and State 4, maximum stimulation being equal to that obtained with an uncoupler of oxidative phosphorylation. Under all circumstances, phloretin lowered the transmembrane electrical potential difference in isolated mitochondria. These results are discussed in terms of mosaic non-equilibrium thermodynamics. We conclude that phloretin is both an uncoupler and an inhibitor of oxidative phosphorylation. 相似文献
19.
The extreme halophile Halobacterium species NRC-1 overcomes external near-saturating salt concentrations by accumulating intracellular salts comparable to those of the medium. This raises the fundamental question of how halophiles can maintain the specificity of protein-nucleic acid interactions that are particularly sensitive to high salts in mesophiles. Here we address the specificity of the essential aminoacylation reaction of the halophile, by focusing on molecular recognition of tRNA(Cys) by the cognate cysteinyl-tRNA synthetase. Despite the high salt environments of the aminoacylation reaction, and despite an unusual structure of the tRNA with an exceptionally large dihydrouridine loop, we show that aminoacylation of the tRNA proceeds with a catalytic efficiency similar to that of its mesophilic counterparts. This is manifested by an essentially identical K(m) for tRNA to those of the mesophiles, and by recognition of the same nucleotide determinants that are conserved in evolution. Interestingly, aminoacylation of the halophile tRNA(Cys) is more closely related to that of bacteria than eukarya by placing a strong emphasis on features of the tRNA tertiary core. This suggests an adaptation to the highly negatively charged tRNA sugar-phosphate backbone groups that are the key elements of the tertiary core. 相似文献
20.
European Journal of Wildlife Research - Art und Verlauf von Verbißschäden durch Fasanen an Tabakpflanzen wurden in Volieren untersucht. Bei Fehlen von Grünäsung nahmen die... 相似文献