scholarly journals Multi-frequency passive and active microrheology with optical tweezers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Randhir Kumar ◽  
Valerio Vitali ◽  
Timo Wiedemann ◽  
Robert Meissner ◽  
Paolo Minzioni ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
A Priori ◽  
Viscous Medium ◽  
Short Time Scale ◽  
Temporal And Spatial ◽  
Force Calibration ◽  
Short Time ◽  
Standard Laser ◽  
Significant Attention

AbstractOptical tweezers have attracted significant attention for microrheological applications, due to the possibility of investigating viscoelastic properties in vivo which are strongly related to the health status and development of biological specimens. In order to use optical tweezers as a microrheological tool, an exact force calibration in the complex system under investigation is required. One of the most promising techniques for optical tweezers calibration in a viscoelastic medium is the so-called active–passive calibration, which allows determining both the trap stiffness and microrheological properties of the medium with the least a-priori knowledge in comparison to the other methods. In this manuscript, we develop an optimization of the active–passive calibration technique performed with a sample stage driving, whose implementation is more straightforward with respect to standard laser driving where two different laser beams are required. We performed microrheological measurements over a broad frequency range in a few seconds implementing an accurate multi-frequency driving of the sample stage. The optical tweezers-based microrheometer was first validated by measuring water, and then exemplarily applied to more viscous medium and subsequently to a viscoelastic solution of methylcellulose in water. The described method paves the way to microrheological precision metrology in biological samples with high temporal- and spatial-resolution allowing for investigation of even short time-scale phenomena.

Rapid adaptation of intestinal glucose transport: a brush-border or basolateral phenomenon?

1987 ◽  
Vol 253 (1) ◽  
pp. G54-G61 ◽  
Author(s):  
W. H. Karasov ◽  
E. S. Debnam
Keyword(s):  
Glucose Transport ◽  
Brush Border ◽  
Basolateral Membrane ◽  
Glucose Absorption ◽  
Short Time Scale ◽  
Rapid Adaptation ◽  
Significant Difference ◽  
Short Time

Regulation of intestinal nutrient absorption can occur on a very short time scale (i.e., 3–5 h). In this study we set out to determine whether this phenomenon of very rapid adaptation is mediated by changes at the level of the brush-border or basolateral membrane of enterocyte. We employed two experimental manipulations that had been reported to cause increased glucose transport in jejunum within as short a time as 3 h: 1) hyperglycemia caused by jugular vein infusion of glucose, and 2) perfusion of the ileal lumen with glucose. We measured glucose absorption by two methods. 1) An in vitro method that tested directly for an effect at the brush border of enterocytes, and 2) an in vivo method whose measurement is a composite phenomenon including events at both boundaries of enterocytes. Carrier-mediated D-glucose absorption in jejunum in vivo was significantly enhanced by approximately 60% in both experimental situations, but there was no significant difference in in vitro unidirectional uptake at the brush border of tissues removed from the same region of the jejunum. The experimental manipulations also had no effect on glucose uptake by brush-border membranes in the other regions of the gut, nor on the passive uptake of L-glucose or the total uptake of L-proline. These results, plus a comparison of the Vmax values for glucose absorption in vitro and in vivo suggest the following: 1) in the “nonadapted” (i.e., control) rats the rate-limiting step in glucose absorption in vivo is efflux at the basolateral membrane, and 2) the observed rapid increase in glucose absorption in vivo appears to be mediated by change at the level of the basolateral membrane.

scholarly journals Characteristics of human mobility patterns revealed by high-frequency cell-phone position data

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Chen Zhao ◽  
An Zeng ◽  
Chi Ho Yeung
Keyword(s):  
High Frequency ◽  
Cell Phone ◽  
Human Mobility ◽  
Short Time Scale ◽  
Mobility Patterns ◽  
Transition Mechanism ◽  
Position Data ◽  
Temporal And Spatial ◽  
The Individual ◽  
Short Time

AbstractHuman mobility is an important characteristic of human behavior, but since tracking personalized position to high temporal and spatial resolution is difficult, most studies on human mobility patterns rely on sparsely sampled position data. In this work, we re-examined human mobility patterns via comprehensive cell-phone position data recorded at a high frequency up to every second. We constructed human mobility networks and found that individuals exhibit origin-dependent, path-preferential patterns in their short time-scale mobility. These behaviors are prominent when the temporal resolution of the data is high, and are thus overlooked in most previous studies. Incorporating measured quantities from our high frequency data into conventional human mobility models shows inconsistent statistical results. We finally revealed that the individual preferential transition mechanism characterized by the first-order Markov process can quantitatively reproduce the observed travel patterns at both individual and population levels at all relevant time-scales.

Periodic Variations in the Coronal Green Line Intensity and their Connection with the White-light Coronal Structures

2000 ◽  
Vol 179 ◽  
pp. 197-200
Author(s):  
Milan Minarovjech ◽  
Milan Rybanský ◽  
Vojtech Rušin
Keyword(s):  
Time Resolution ◽  
White Light ◽  
Short Time Scale ◽  
High Time Resolution ◽  
Green Line ◽  
Periodic Intensity ◽  
Coronal Green Line ◽  
Significant Intensity ◽  
Short Time ◽  
Coronal Structures

AbstractWe present an analysis of short time-scale intensity variations in the coronal green line as obtained with high time resolution observations. The observed data can be divided into two groups. The first one shows periodic intensity variations with a period of 5 min. the second one does not show any significant intensity variations. We studied the relation between regions of coronal intensity oscillations and the shape of white-light coronal structures. We found that the coronal green-line oscillations occur mainly in regions where open white-light coronal structures are located.

Rapid, Refined, and Robust Method for Expression, Purification, and Characterization of Recombinant Human Amyloid-beta M1-42

2019 ◽  
Author(s):  
Priya Prakash ◽  
Travis Lantz ◽  
Krupal P. Jethava ◽  
Gaurav Chopra
Keyword(s):  
Amyloid Beta ◽  
Western Blots ◽  
Force Microscopy ◽  
E Coli ◽  
Atomic Force ◽  
Set Up ◽  
Short Time

Amyloid plaques found in the brains of Alzheimer’s disease (AD) patients primarily consists of amyloid beta 1-42 (Ab42). Commercially, Ab42 is synthetized using peptide synthesizers. We describe a robust methodology for expression of recombinant human Ab(M1-42) in Rosetta(DE3)pLysS and BL21(DE3)pLysS competent E. coli with refined and rapid analytical purification techniques. The peptide is isolated and purified from the transformed cells using an optimized set-up for reverse-phase HPLC protocol, using commonly available C18 columns, yielding high amounts of peptide (~15-20 mg per 1 L culture) in a short time. The recombinant Ab(M1-42) forms characteristic aggregates similar to synthetic Ab42 aggregates as verified by western blots and atomic force microscopy to warrant future biological use. Our rapid, refined, and robust technique to purify human Ab(M1-42) can be used to synthesize chemical probes for several downstream in vitro and in vivo assays to facilitate AD research.

ECONOMIC PERSPECTIVES OF BIOTECHNOLOGIES USING IN ANIMAL FARMING

1970 ◽  
pp. 57-60
Author(s):  
I. F. Gorlov ◽  
A. A. Mosolov ◽  
G. V. Komlatskiy ◽  
M. A. Nesterenko ◽  
K. D. Nimbona ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Economic Effect ◽  
Dairy Herd ◽  
State Level ◽  
Modern Level ◽  
Economic Perspectives ◽  
The Cost ◽  
Short Time

The article presents materials on the study of the possibility of reproduction and increase in the herd of highly productive cows through the use of embryo transplantation technology. The classical (in vivo) and more modern, developing (in vitro) methods of embryotransfer, their positive and negative sides are considered in detail. The possibility of accelerating the breeding process by using the method of transplantation, in which from one cow can be obtained from 10 to 100 calves, which will allow for 4-5 years, almost any herd (of any size and breed) with the help of biotechnology to turn into a cattle-breeding enterprise of the most modern level. At the same time, heifers obtained from unproductive cows can be used as "surrogate" mothers who are transplanted with the best donor embryos, which allows to obtain a full-fledged offspring adapted to local environmental conditions. A detailed scheme of obtaining, evaluation, storage, as well as the cost and economic effect of embryo transplantation was calculated, the market was evaluated, the required annual volume of transplants and the number of donor cows for large livestock farms were determined. As a positive example of "Scientific-production enterprise "Centre of biotechnology and embryo transfer" in 2014, implemented a project for accelerated replacement and genetic improvement of the dairy herd, engraftment averaged 57-69%, and the economic effect of the enterprise from getting a single animal by the method of embryo transfer, compared with imports of similar close in quality, ranged from 60 to 100 thousand rubles on his head. It is shown that it is necessary to organize at the state level a developed service for embryo transplantation to reduce the cost of embryo transfer and the possibility of creating in a short time in the country's own highly productive breeding nucleus of dairy and beef cattle, which will reduce, and in the future completely eliminate, import dependence on cattle products.

Nondiffusive Brownian Motion Studied by Diffusing-Wave Spectroscopy

1989 ◽  
Vol 177 ◽  
Author(s):  
D. J. Pine ◽  
D. A. Weitz ◽  
D. J. Durian ◽  
P. N. Pusey ◽  
R. J. A. Tough
Keyword(s):  
Autocorrelation Function ◽  
Colloidal Particles ◽  
Scattered Light ◽  
Short Time Scale ◽  
Velocity Autocorrelation Function ◽  
Velocity Autocorrelation ◽  
Power Law Decay ◽  
Brownian Particles ◽  
Short Time ◽  
Surrounding Fluid

ABSTRACTOn a short time scale, Brownian particles undergo a transition from initially ballistic trajectories to diffusive motion. Hydrodynamic interactions with the surrounding fluid lead to a complex time dependence of this transition. We directly probe this transition for colloidal particles by measuring the autocorrelation function of multiply scattered light and observe the effects of the slow power-law decay of the velocity autocorrelation function.

scholarly journals In vivo interactome profiling by enzyme‐catalyzed proximity labeling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yangfan Xu ◽  
Xianqun Fan ◽  
Yang Hu
Keyword(s):  
State Of The Art ◽  
Catalytic Efficiency ◽  
Biological Processes ◽  
Protein Protein Interaction ◽  
Current State ◽  
Protein Interactome ◽  
Potential Applications ◽  
Protein Protein Interaction Networks ◽  
Temporal And Spatial

AbstractEnzyme-catalyzed proximity labeling (PL) combined with mass spectrometry (MS) has emerged as a revolutionary approach to reveal the protein-protein interaction networks, dissect complex biological processes, and characterize the subcellular proteome in a more physiological setting than before. The enzymatic tags are being upgraded to improve temporal and spatial resolution and obtain faster catalytic dynamics and higher catalytic efficiency. In vivo application of PL integrated with other state of the art techniques has recently been adapted in live animals and plants, allowing questions to be addressed that were previously inaccessible. It is timely to summarize the current state of PL-dependent interactome studies and their potential applications. We will focus on in vivo uses of newer versions of PL and highlight critical considerations for successful in vivo PL experiments that will provide novel insights into the protein interactome in the context of human diseases.

scholarly journals On the Short Time Scale Evolutionary History of the Contact Binary VW Cephei

1998 ◽  
Vol 11 (1) ◽  
pp. 396-396
Author(s):  
I. Pustylnik
Keyword(s):  
Evolutionary History ◽  
Light Curves ◽  
Published Data ◽  
Short Time Scale ◽  
Flare Activity ◽  
Considerable Portion ◽  
History Of ◽  
Contact Binary ◽  
Elongation Phase ◽  
Short Time

We study the short-time evolutionary history of the well-known contact binary VW Cep. Our analysis is based partly on the numerous UBV lightcurves obtained at Tartu Observatory, IUE spectra, and samples from the published data. Special attention is given to the effects of asymmetry of the light curves. A higher degree of asymmetry outside the eclipses along with the significant displacements of the brightness maxima in respect to the elongation phase is interpreted as evidence that a considerable portion of the flaring source is concentrated close to the neck connecting the components. We discuss the nature of asymmetry in terms of possible mass exchange and the flare activity and compare the results of our model computations with the record of orbital period variations over the last 60 years.

scholarly journals Aerosol-based antimicrobial photoinactivation in the lungs: an action spectrum study

2021 ◽  
Author(s):  
Chiara Treghini ◽  
Alfonso Dell’Accio ◽  
Franco Fusi ◽  
Giovanni Romano
Keyword(s):  
Light Source ◽  
A Priori ◽  
Action Spectrum ◽  
Multidrug Resistant ◽  
Theoretical Modelling ◽  
Resistant Bacteria ◽  
Lung Infections ◽  
Killing Action ◽  
Definition Of

AbstractChronic lung infections are among the most diffused human infections, being often associated with multidrug-resistant bacteria. In this framework, the European project “Light4Lungs” aims at synthesizing and testing an inhalable light source to control lung infections by antimicrobial photoinactivation (aPDI), addressing endogenous photosensitizers only (porphyrins) in the representative case of S. aureus and P. aeruginosa. In the search for the best emission characteristics for the aerosolized light source, this work defines and calculates the photo-killing action spectrum for lung aPDI in the exemplary case of cystic fibrosis. This was obtained by applying a semi-theoretical modelling with Monte Carlo simulations, according to previously published methodology related to stomach infections and applied to the infected trachea, bronchi, bronchioles and alveoli. In each of these regions, the two low and high oxygen concentration cases were considered to account for the variability of in vivo conditions, together with the presence of endogenous porphyrins and other relevant absorbers/diffusers inside the illuminated biofilm/mucous layer. Furthermore, an a priori method to obtain the “best illumination wavelengths” was defined, starting from maximizing porphyrin and light absorption at any depth. The obtained action spectrum is peaked at 394 nm and mostly follows porphyrin extinction coefficient behavior. This is confirmed by the results from the best illumination wavelengths, which reinforces the robustness of our approach. These results can offer important indications for the synthesis of the aerosolized light source and definition of its most effective emission spectrum, suggesting a flexible platform to be considered in further applications.

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