phase transition
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Our study demonstrates that nanoplasmonic sensing (NPS) can be utilized for the determination of the phase transition temperature (Tm) of phospholipids. During the phase transition, the lipid bilayer undergoes a conformational change. Therefore, it is presumed that the Tm of phospholipids can be determined by detecting conformational changes in liposomes. The studied lipids included 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). Liposomes in gel phase are immobilized onto silicon dioxide sensors and the sensor cell temperature is increased until passing the Tm of the lipid. The results show that, when the system temperature approaches the Tm, a drop of the NPS signal is observed. The breakpoints in the temperatures are 22.5 °C, 41.0 °C, and 55.5 °C for DMPC, DPPC, and DSPC, respectively. These values are very close to the theoretical Tm values, i.e., 24 °C, 41.4 °C, and 55 °C for DMPC, DPPC, and DSPC, respectively. Our studies prove that the NPS methodology is a simple and valuable tool for the determination of the Tm of phospholipids.
Purpose of this paper is to describe characteristic features of dissolution data by using homogeneous model of dissolution with initial transient phase. To achieve the goal we consider a random lag time before the homogeneous phase of the dissolution begins. The resulting dissolution profiles are characterized by sigmoidal shape commonly observed in empirical dissolution data. Furthermore, probability distribution of repeated measurements at fixed time is deduced from the model and function describing variability of the data in dependency on time is proposed. Three examples with normal, exponential and gamma probability distribution of the lag time are presented. All the models are pairwise compared with the Weibull function with high similarity between them. The result offers an alternative interpretation for the frequently found fit of the Weibull model to experimental data.
SIGNIFICANCE: Machine learning is increasingly being applied to the classification of microscopic data. In order to detect some complex and dynamic cellular processes, time-resolved live-cell imaging might be necessary. Incorporating the temporal information into the classification process may allow for a better and more specific classification. AIM: We propose a methodology for cell classification based on the time-lapse quantitative phase images (QPIs) gained by digital holographic microscopy (DHM) with the goal of increasing performance of classification of dynamic cellular processes. APPROACH: The methodology was demonstrated by studying epithelial-mesenchymal transition (EMT) which entails major and distinct time-dependent morphological changes. The time-lapse QPIs of EMT were obtained over a 48-h period and specific novel features representing the dynamic cell behavior were extracted. The two distinct end-state phenotypes were classified by several supervised machine learning algorithms and the results were compared with the classification performed on single-time-point images. RESULTS: In comparison to the single-time-point approach, our data suggest the incorporation of temporal information into the classification of cell phenotypes during EMT improves performance by nearly 9% in terms of accuracy, and further indicate the potential of DHM to monitor cellular morphological changes. CONCLUSIONS: Proposed approach based on the time-lapse images gained by DHM could improve the monitoring of live cell behavior in an automated fashion and could be further developed into a tool for high-throughput automated analysis of unique cell behavior.
The freezing process consists of dissipating heat from the product until the final temperature is lower than the temperature of crystallisation of that product. Freezing can be used for numerous applications, including for disruption of waste-activated sludge (WAS). The aim of this study was to calculate the estimated amount of heat conveyed between the solidified carbon dioxide and the WAS, in the following ratios: 0.25:1; 0.5:1; 0.75:1 and 1:1. In heat of phase transformations, dry ice sublimation, water solidification, the amount of heat transferred by other substances and heat transferred from the sludge (dry sludge) were taken into account during the process of WAS freezing. Heat changes on the surface of WAS were registered using a thermovision camera. The effectiveness of WAS disintegration was confirmed by several biochemical parameters such as soluble chemical oxygen demand (increase over 14 times), degree of disintegration (48%), proteins (increase over 5 times), carbohydrates (increase almost 7 times), RNA (increase by 2.23 mg L-1), ammonia nitrogen (increase over 23 times), phosphates (increase almost 27 times) and turbidity (increased over 7 times). It was found that dry ice pretreatment of WAS can be an intriguing alternative for the conventional methods used.
Vapor phase hydrogen peroxide (VPHP) nowadays finds more and more applications especially as a bio-decontamination agent for enclosed areas. Although this oxidizing agent logically offers a potential for the degradation of hazardous chemical contaminants, the information on the utilization within this area is very limited. The main objective of this study was to examine in detail the influence of basic operational (temperature, concentration of VPHP, relative humidity, condensation) and other conditions (e.g. amount of contaminant, the effect of UV radiation) on the efficiency of the VPHP process for the degradation of the selected model substance, i.e. 4-(dimethylamino)benzaldehyde. For this purpose, a series of different VPHP "wet" decontamination cycles (with a visible condensation) were carried out and compared. The obtained results clearly proved that VPHP could be utilized for the degradation of 4-(dimethylamino)benzaldehyde, however it was necessary to regard this process as a multi-parametric, in which all operational conditions played significant roles, while the molecular distribution of H(2)O and H(2)O(2) at first constituted the key factor for a successful degradation of contaminants on the surface. In order to achieve the highest decomposition efficiency of 4-(dimethylamino)benzaldehyde by the wet VPHP process, it appeared to be necessary to decrease the initial relative humidity in the relevant enclosed area (ideally up to 5%) before the introduction of VPHP and carry out this decontamination procedure ideally at 25°C and maintain the VPHP concentration higher than 500 ppm. Furthermore, it was found that the addition of UV radiation had a positive role on VPHP efficiency (in the best case, the degradation rate increased up to 1.5 times compared to using the sole VPHP). The monitoring of the concentration of VPHP within an enclosed facility is a good tool for the monitoring of the degradation of chemical contaminants by this agent.
- MeSH
- benzaldehydy analýza chemie MeSH
- chemické modely MeSH
- indikátory a reagencie analýza chemie MeSH
- látky znečišťující životní prostředí analýza chemie MeSH
- peroxid vodíku chemie MeSH
- regenerace a remediace životního prostředí metody MeSH
- teplota MeSH
- změna skupenství MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The fluorescent molecule diphenylhexatriene (DPH) has been often used in combination with fluorescence anisotropy measurements, yet little is known regarding the non-linear optical properties. In the current work, we focus on them and extend the application to fluorescence, while paying attention to the conformational versatility of DPH when it is embedded in different membrane phases. Extensive hybrid quantum mechanics/molecular mechanics calculations were performed to investigate the influence of the phase- and temperature-dependent lipid environment on the probe. Already, the transition dipole moments and one-photon absorption spectra obtained in the liquid ordered mixture of sphingomyelin (SM)-cholesterol (Chol) (2:1) differ largely from the ones calculated in the liquid disordered DOPC and solid gel DPPC membranes. Throughout the work, the molecular conformation in SM:Chol is found to differ from the other environments. The two-photon absorption spectra and the ones obtained by hyper-Rayleigh scattering depend strongly on the environment. Finally, a stringent comparison of the fluorescence anisotropy decay and the fluorescence lifetime confirm the use of DPH to gain information upon the surrounding lipids and lipid phases. DPH might thus open the possibility to detect and analyze different biological environments based on its absorption and emission properties.
- MeSH
- cholesterol chemie MeSH
- difenylhexatrien chemie MeSH
- fluorescenční barviva chemie MeSH
- fluorescenční polarizace MeSH
- lipidové dvojvrstvy chemie MeSH
- molekulární konformace MeSH
- sfingomyeliny chemie MeSH
- simulace molekulární dynamiky MeSH
- tranzitní teplota MeSH
- vztahy mezi strukturou a aktivitou MeSH
- změna skupenství MeSH
- Publikační typ
- časopisecké články MeSH
