PubMed Health⌕ Search

Biomedical subjects

Jiang Zhao

Publications and source records attributed to Jiang Zhao.

15 recordsLinked to original sources
PubMed2005

New method for determining tie-lines in coexisting membrane phases using spin-label ESR.

A full description of coexisting phases includes their respective compositions, which are provided by the thermodynamic tie-lines. Fluorescence microscopy enables visualization of coexisting lipid phases in giant unilamellar phases, but the composition information is missing. For cholesterol-containing lipid mixtures, knowledge of the compositions of the coexisting phases is important for understanding the nature of "membrane rafts". We propose and demonstrate a new method, based on ESR spectroscopy, for determining tie-lines in regions of two-phase coexistence in a ternary lipid mixture. Over 100 different lipid compositions containing the spin-labeled phospholipid 16-PC in or near the two-phase coexistence region of the liquid-disordered and the gel phases of dipalmitoyl-PC/dilauroyl-PC/cholesterol (DPPC/DLPC/Chol) were studied to determine five tie-lines, spread over virtually the full range of this coexistence region. The method is based on the facts that (1) along a tie-line the ESR spectrum must be a superposition of the two ESR spectra from the respective single phases at the phase boundaries (connected by the tie-line) in a ratio given by the lever rule; (2) along a tie-line the partition coefficient, K(p), for the spin-label, which is also determined in our method, must be constant. We do find that K(p) for 16-PC is close to unity, but its value depends on the particular tie-line. The coexisting phases in equilibrium are characterized by the K(p) of the spin-label and its respective dynamic parameters obtained from fitting the ESR spectra to dynamical models.

Cholesterol↗
PubMed2005

[Foraging habitat selection of Otis tarda dybowskil during its breeding season].

From April to July of 2000 and 2001, the authors studied the foraging habitat selection of Otis tarda dybowskil in the southeast Keerqin of Inner Mongolia by sampling method. The results showed that whether at burned or at non-burned grassland, the foraging habitat of Otis tarda dybowski had the same feature in vegetation structure, the plant height was about 13 cm on average, with the highest of 30 cm, and there were abundant species of plants and insects with big density that the bird favored to eat. The bird more concerned with the abundance of plants at burned grassland, while that of insects at non-burned grassland.

Animals↗
PubMed2004

How confined lubricants diffuse during shear.

The translational diffusion of a fluorescent dye embedded at a dilute concentration in a confined fluid was compared at rest and during shear. The fluid, octamethylcyclotetrasiloxane (OMCTS), was confined between step-free muscovite mica to thickness 3-4 layers. Fluorescence correlation spectroscopy showed that the time scales of intensity-intensity autocorrelation functions were essentially the same during shear and at rest, except they were faster during shear by a factor of 2 to 5. This dynamical probe of how liquids order in molecularly thin films fails to support the hypothesis that shear produced a melting transition.

Journal Article↗
PubMed2004

Polymer lateral diffusion at the solid-liquid interface.

Measurements are presented of how polymer surface diffusion at the solid-liquid interface is controlled by surface coverage. The method of measurement was fluorescence correlation spectroscopy (FCS), and the system was poly(ethylene oxide) (PEG) adsorbed onto methyl-terminated self-assembled monolayers in buffered aqueous solution. The translational diffusion coefficient at first increased with increasing surface concentration, presumably because the number of adsorption sites per molecule decreased. Ultimately it slowed by 1 order of magnitude, presumably reflecting jamming by neighboring chains.

Journal Article↗
PubMed2004

[Dynamics of nutrient element iron in soil-plant ecosystem of the Songnen Plain Leymus chinensis grassland].

The study showed that in the soil-plant ecosystem of the Songnen Plain Leymus chinensis grassland, the contents of total and available iron in soil were relatively low, while Leymus chinensis was abundant in iron. The concentrations of soil total and available iron decreased with soil depth. Soil available iron positively correlated with soil organic matter, while negatively correlated with soil pH. The dynamics of soil total iron showed a "V" curve during the growth season, with the lowest in July, and that of soil available iron was similar to soil total iron from May to August, and gradually decreased after August. The iron concentration in Leynus chinensis changed dramatically with the trend of root > rhizome > leaf > litter > stem. The iron concentrations in leaf and stem had a fluctuant decrease, while those in root, rhizome and litter were fluctuated in "V" curve. Soil A layer enriched in a little more available iron. The iron activation with an average of 0.64% increased from May to August, and decreased after August, with the lowest in October. The shift ratio from underground to aboveground part of Leymus chinensis dropped during May-July, went up in August, and then dropped again. The average shift ratio from aboveground part to litter was 105.0%, which negatively correlated with that from underground to aboveground part.

China↗
PubMed2003

Probing Ca2+-induced conformational changes in porcine calmodulin by H/D exchange and ESI-MS: effect of cations and ionic strength.

We applied a new method, "protein-ligand interaction using mass spectrometry, titration, and H/D exchange" (PLIMSTEX) [Zhu, M. M. (2003) J. Am. Chem. Soc. 125, 5252-5253], to determine the conformational changes, binding stoichiometry, and binding constants for Ca(2+) interactions with calmodulin (CaM) under varying conditions of electrolyte identity and ionic strength. The outcome shows that CaM becomes less solvent-accessible and more compact upon Ca(2+)-binding, as revealed by the PLIMSTEX curve. The formation of CaM-4Ca species is the biggest contributor to the shape of the titration curve, indicating that the formation of this species accounts for the largest conformational change in the stepwise Ca(2+) binding. The Ca(2+)-binding constants, when comparisons permit, agree with those in the literature within a factor of 3. The binding is influenced by ionic strength and the presence of other cations, although many of these cations do not cause conformational change in apo-CaM. Furthermore, Ca(2+)-saturated CaM exhibits larger protection and higher Ca(2+) affinity in media of low rather than high ionic strength. Both Ca(2+) and Mg(2+) bind to CaM with different affinities, causing different conformational changes. K(+), if it does bind, causes no detectable conformational change, and interactions of Ca(2+) with CaM in the presence of Li(+), Na(+), and K(+) occur with similar affinities and associated changes in solvent accessibility. These metal ion effects point to nonspecific rather than competitive binding of alkali-metal ions. The rates of deuterium uptake by the various CaM-xCa species follow a three-group (fast, intermediate, slow), pseudo-first-order kinetics model. Calcium binding causes the number of amide hydrogens to shift from the fast to the slow group. The results taken together not only provide new insight into CaM but also indicate that both PLIMSTEX and kinetic modeling of H/D exchange data may become general methods for probing protein conformations and quantifying protein-ligand interactions.

Animals↗
PubMed2003

[Extract non-point pollution source information from a TM image by hierarchical classification].

The issue of the article is hierarchical classification that is used to extract land-use information relating to non-point source pollution from TM image. The result shows that it performs better than traditional maximum likelihood method. It is useful to extract information quickly and effectively with advantages of simplifying complex problem, giving prominence to key point and having more flexibility.

Agriculture↗
PubMed2003

[Behaviors time budget and daily rhythm of great bustard in breeding season].

The direct observation method was adopted to study the breeding behaviors time budget and daily rhythm of wild great bustard (Otis tarda) on the grassland of Southeast Keyouqianqi in Inner Mongolia Municipality during the period from April to July in 2000 and 2001. The results showed that the behaviors time budget of great bustard were regularly in some degree, and there exited differences between male and female. The behaviors changed with the changes of activity space, food conditions and breeding stages. During breeding prophase, great bustard spent its time mainly on feeding, relaxing, walking and observing, and the male and female spent 87% and 93% of the time on the 4 behaviors, respectively. The time budget and intensity of male and female changed greatly during the breeding anaphase. The great bustard had a daily rhythm on feeding, relaxing and displaying, and there were two peaks on feeding and displaying. The great bustard spent most time on relaxing.

Animals↗
PubMed2002

Contrasting friction and diffusion in molecularly thin confined films.

We study, using fluorescence correlation spectroscopy, translational diffusion in molecularly thin liquids confined within a surface forces apparatus. The diffusion coefficient decreases exponentially from the edges towards the center of the Hertzian contact and further suggests the presence of a small number of distinct diffusion processes. This holds alike a crystallizable fluid (OMCTS) and a glass-former (1,2-propane diol), both of which displayed static friction. We conclude that friction, the average of an ensemble of molecules, masked massively heterogeneous molecular mobility.

Journal Article↗
PubMed2002

High-throughput liquid chromatography ultraviolet/mass spectrometric analysis of combinatorial libraries using an eight-channel multiplexed electrospray time-of-flight mass spectrometer.

We report a high-throughput liquid chromatography/mass spectrometry (LC/MS) protocol for analyzing large combinatorial libraries using an eight-channel parallel LC/UV/MS (MUX-LCT) system. System configuration, linear response range in UV absorbance, LC column selection, and flow rate were optimized for 24 h/7 day unattended operations. Combinatorial libraries were analyzed on this system at a rate of 3200 compounds per day for a 3.5 min cycle time per injection. This parallel system is compared with a single-channel system in terms of performance and operation.

Journal Article↗
PubMed2002

Surface activity of tear fluid in patients with primary Sjögren's syndrome.

Rupture of the preocular tear film leads to formation of a dry spot on the cornea with ocular irritation and symptoms of dry eye. One of the factors determining the stability of the tear film is its surface activity. The purpose of this study was to examine the surface activity of tear fluid from patients with Sjögren's syndrome. Tear fluid was sampled from the eyes of 16 patients with primary Sjogren's syndrome. The surface activity of the sample was measured on a Wilhelmy balance. Maximum and minimum surface tension was 72.2+/-1.7 and 52.9+/-7.4 mN m(-1), respectively. Corresponding values in a previously studied group of normal subjects were 71.5+/-1.3 and 46.6+/-3.8 mN m(-1), respectively. The difference in minimal surface tension was statistically significant (P<0.001). Reduced surface activity may be caused by dysfunction of the Meibomian glands and suggests a mechanism for causing the symptoms of dry eyes.

Adolescent↗
PubMed2002

[On nest-site selection of Otic tarda].

During April to July in 2000 and 2001, the nest-site selection of Otis tarda was studied by direct observation and sampling method in the southeast grassland of Keyouqianqi in Inner Mongolia. The results showed that Otis tarda was one kind of big-sized bird built nests on the ground in sparse cluster, and the smallest distance between nests was 9 m. Otis tarda had a significant tendency in nest-site selection. Firstly, this tendency was represented under the scale of landscape. Most nests of Otis tarda were built on the mid-hill of grassland, the elevation range was from 190 m to 230 m, most nests built on the slopes faced to sun, and the biggest gradient was not more than 8 degree. Moreover, the nests were near to roads. Secondly, Otis tarda selected its nest-site according to vegetation structure. It tended to select nest-site with thick hay, high vegetation density and grass height from 15 cm to 35 cm, but would not select the place with over high vegetation density no nest.

Animals↗
PubMedDate not supplied

High-throughput purification of combinatorial libraries I: a high-throughput purification system using an accelerated retention window approach.

We have developed a high-throughput purification system to purify combinatorial libraries at a 50-100-mg scale with a throughput of 250 samples/instrument/day. We applied an accelerated retention window method to shorten the purification time and targeted one fraction per injection to simplify data tracking, lower QC workload, and simplify the postpurification processing. First, we determined the accurate retention time and peak height for all compounds using an eight-channel parallel LC/UV/MS system, and calculated the specific preparative HPLC conditions for individual compounds. The preparative HPLC conditions include the compound-specific gradient segment for individual compounds with a fixed gradient slope and the compound-specific UV or ELSD threshold for triggering a fraction collection device. A unique solvent composition or solvent strength was programmed for each compound in the preparative HPLC in order to elute all compounds at the same target time. Considering the possible deviation of the predicted retention time, a 1-min window around the target time was set to collect peaks above a threshold based on UV or ELSD detection. Dual column preparative instruments were used to maximize throughput. We have purified more than 500 000 druglike compounds using this system in the past 3 years. We report various components of this high-throughput purification system and some of our purification results.

Journal Article↗