Energy metabolism design of the striated muscle cell.

The design of the energy metabolism system in striated muscle remains a major area of investigation. Here, we review our current understanding and emerging hypotheses regarding the metabolic support of muscle contraction. Maintenance of ATP free energy, so called energy homeostasis, via mitochondrial oxidative phosphorylation is critical to sustained contractile activity, and this major design criterion is the focus of this review. Cell volume invested in mitochondria reduces the space available for generating contractile force, and this spatial balance between mitochondria acontractile elements to meet the varying sustained power demands across muscle types is another important design criterion. This is accomplished with remarkably similar mass-specific mitochondrial protein composition across muscle types, implying that it is the organization of mitochondria within the muscle cell that is critical to supporting sustained muscle function. Beyond the production of ATP, ubiquitous distribution of ATPases throughout the muscle requires rapid distribution of potential energy across these large cells. Distribution of potential energy has long been thought to occur primarily through facilitated metabolite diffusion, but recent analysis has questioned the importance of this process under normal physiological conditions. Recent structural and functional studies have supported the hypothesis that the mitochondrial reticulum provides a rapid energy distribution system via the conduction of the mitochondrial membrane potential to maintain metabolic homeostasis during contractile activity. We extensively review this aspect of the energy metabolism design contrasting it with metabolite diffusion models and how mitochondrial structure can play a role in the delivery of energy in the striated muscle.

Fast vibrational analysis of molecular systems.

The development of infrared difference spectroscopy provides unprecedented insights on structures of complex molecules like metalloproteins. However, the relevant information can be hard to find among the many bands of the vibrational spectra. The ab initio modeling is very helpful to assign the frequencies to vibrational modes but it is a challenge to process the huge quantity of data into descriptors useful for experimentalists. To this end, we developed a new tool called VIBMOL allowing to analyze vibrational modes of molecules from hessian matrices calculated with common quantum chemistry codes. VIBMOL program runs on Unix machines. Through a new graphical interface, the users can calculate the normal modes of molecules, visualize them, simulate infrared spectra, and explore the Potential Energy Distribution of normal modes among any set of vibration coordinates. It is combined with an interface program (gosdmu) formatting relevant data from the GAUSSIAN program. VIBMOL code is available upon request to the authors. A discussion is provided to help the readers to choose between a large choice of different software and it shows how VIBMOL can make the IR assignment easier in the context of collaborations with experimentalists.

The role of nuclear fragmentations in high energy transfers to a micro-object exposed to primary space radiation.

This paper describes events of anomalously high energy transfer to a micro-object by fragments of nuclei generated in nuclear interactions in the environment on board a spacecraft in flight in low-Earth orbit. An algorithm has been developed that allows for the calculation of the absorbed energy from one or more fragments - products of nuclear interaction. With this algorithm the energy distributions for a spherical micro-volume in an aqueous medium were calculated. And the resulting absorbed energy spectra from nuclear fragments and from primary cosmic rays were compared. The role of nuclear interactions in events of large energy transfers in micro-objects in the field of primary cosmic radiation has been evaluated. The calculations performed in this study showed that the energy in a micro-volume from nuclear events can be several times higher compared to the energy imparted by primary space radiation.

Screening and analysis of the targeted compounds in Choerospondias axillaris extract by receptor chromatographic column with immobilized angiotensin II type 1 receptor.

As a result of the lack of modern techniques, the study of Tibetan medicine has been hindered in identifying bioactive compounds. Herein, we established a chromatographic approach using an immobilized angiotensin II type 1 receptor (AT1R) via a one-step method triggered by haloalkane dehalogenase. The bioactive compounds from Choerospondias axillaris (Guangzao) were screened and identified using the immobilized AT1R followed by MS. Frontal analysis (FA) and adsorption energy distribution (AED) were used to evaluate the association constants. Molecular docking was used to investigate the binding configurations, and the surface efficiency index, binding efficiency index, and ligand-lipophilicity efficiency (LLE) were calculated to assess the drug-like properties. The results identified naringenin, pinocembrin, and chrysin as the compounds that specifically bind to AT1R in Guangzao. FA and AED confirmed that there is only one type of binding site between these compounds and AT1R. The association constants were (2.40 ± 0.02) × 104 M-1 for naringenin (5.22 ± 0.26) × 104 M-1 for pinocembrin, and (4.27 ± 0.14) × 104 M-1 for chrysin, respectively. These compounds can bind with AT1R through the orthosteric binding pocket. Naringenin exhibited better LLE than pinocembrin and chrysin. These results confirmed the feasibility of using the immobilized AT1R column for screening and analyzing bioactive compounds in Tibetan medicines.

A Novel Method for Precision Measurement and Result Optimization of Detuning Angle for KDP Crystals.

In this paper, we investigate the theory of energy distribution when divergent light undergoes harmonic conversion in KDP crystals, and based on this theory, we design and construct a precision measuring instrument for the detuning angle of (KDP) Crystals (MIDC). The device can obtain the detuning angle of the crystal by a single measurement with an average measurement error of 72.78 urad. At the same time, it also has the function of scanning the full aperture of the crystals. Using the MIDC, it is possible to quickly measure the KDP crystal at a single point and quickly scan the crystal detuning angle at full aperture. In addition, we conduct a theoretical study on the variation of detuning angle caused by gravity-influencing factors under online conditions, propose an optimization formula for the offline measurement results of detuning angle, and calculate the optimized values of detuning angle for two kinds of crystals under 45° online conditions. We finally study the error source of the MIDC device, analyze the trend of the influence of positioning errors of the crystal and optical elements on the detuning angle measurement results, and provide theoretical support for the error monitoring and correction of MIDC.

Statistical Equivalence of Quantum Chemical Methods for Energy Distribution in Water Clusters.

Methods of quantum chemistry are instrumental in understanding molecular structures and properties. However, the results demonstrate significant variability, which is difficult to predict and rationalize. The fundamental question is whether some molecular systems exhibit properties invariant with respect to the computational method. The idea explored here is that collective properties of statistical ensembles should be more robust than characteristics of individual molecules and their arbitrary sets. This effect is demonstrated for the complete set of hydrogen-bond topologies of the dodecahedral water cluster (H2 O)20 . Non-Gaussian energy distributions produced by various methods have the same functional form despite strong differences in mean values and standard deviations. The conclusion is tested on methods of different complexity and origin employing a number of criteria. A linear mapping between the energies produced by different methods is discussed. The significance of the results is in establishing a collective equivalence property of quantum chemical methods.

Maternal melatonin levels and temporal dietary intake: results from MY-CARE cohort study.

Chrononutrition emerges as a novel approach to promote circadian alignment and metabolic health by means of time-of-the-day dietary intake. However, the relationship between maternal circadian rhythm and temporal dietary intake during pregnancy remains understudied. This study aimed to determine the change in melatonin levels in pregnant women across gestation and its association with temporal energy and macronutrient intake. This was a prospective cohort involving 70 healthy primigravidas. During the second and third trimesters, pregnant women provided salivary samples collected at 9:00, 15:00, 21:00, and 3:00 h over a 24 h day for melatonin assay. Data on chrononutrition characteristics were collected using a 3-day food record. Parameters derived from melatonin measurements including mean, amplitude, maximal level, area under the curve with respect to increase (AUCI), and area under the curve with respect to ground (AUCG) were computed. A rhythmic melatonin secretion over the day that remained stable across trimesters was observed among the pregnant women. There was no significant elevation in salivary melatonin levels as pregnancy advanced. In the second trimester, higher energy intake during 12:00-15:59 h and 19:00-06:59 h predicted a steeper melatonin AUCI (ß=-0.32, p = 0.034) and higher AUCG (ß = 0.26, p = 0.042), respectively. Macronutrient intake within 12:00-15:59 h was negatively associated with mean melatonin (Fat: ß=-0.28, p = 0.041) and AUCG (Carbohydrate: ß=-0.37, p = 0.003; Protein: ß=-0.27, p = 0.036; Fat: ß=-0.32, p = 0.014). As pregnant women progressed from the second to the third trimester, a flatter AUCI was associated with a reduced carbohydrate intake during 12:00-15:59 h (ß=-0.40, p = 0.026). No significant association was detected during the third trimester. Our findings show that higher energy and macronutrient intakes particularly during 12:00-15:59 h and 19:00-06:59 h are associated with the disparities in maternal melatonin levels. Findings suggest the potential of time-based dietary approaches to entrain circadian rhythm in pregnant women.

UCP1 and AOX1a contribute to regulation of carbon and nitrogen metabolism and yield in Arabidopsis under low nitrogen stress.

Nitrogen (N) availability is a critical factor for plant development and crop yield, and it closely correlates to carbon (C) metabolism. Uncoupling protein (UCP) and alternative oxidase (AOX) exhibit a strong correlation with N and C metabolism. Here, we investigated the functions of UCP1 and AOX1a using their mutants and complementation lines in Arabidopsis adaptation to low N. Low N markedly increased AOX1a and UCP1 expression, alternative pathway capacity and UCP activity. Eight-day-old aox1a/ucp1 seedlings were more sensitive to low N than Col-0 and single mutants, exhibiting lower primary root length and higher anthocyanin accumulation. The net photosynthetic rate, electron transport rate, PSII actual photochemical efficiency, stomatal conductance and carboxylation efficiency were markedly decreased in ucp1 and aox1a/ucp1 compared to those in Col-0 and aox1a under low N stress; comparatively, chlorophyll content and non-photochemical quenching coefficient were the lowest and highest in aox1a/ucp1, respectively. Nitrate acquisition rate was accelerated in aox1a/ucp1, but its transport activity was decreased, which resulted in low nitrate content and nitrate reductase activity under low N condition. The C/N ratio in seeds, but not in leaves, is higher in aox1a/ucp1 than that in Col-0, aox1a and ucp1 under low N condition. RNA-seq analysis revealed that many genes involved in photosynthesis and C/N metabolism were markedly down-regulated in aox1a/ucp1 under low N stress. These results highlight the key roles of UCP1 and AOX1a in modulating photosynthetic capacity, C/N assimilation and distribution under low N stress.

Exploring the Potential of a Thermionic LaB6 Virtual Source Mode Electron Gun for a High Angular Current Density and a Narrow Energy Distribution.

To date, lanthanum hexaboride (LaB6) thermionic electron sources have not been able fully to capitalize on their inherent potential, resulting in an ambiguous position within the application area. Although they exhibit higher brightness compared with a tungsten filament source, they still fall short of the performance of Schottky electron sources. This study aims to explore the capabilities of the LaB6 electron source under different operating conditions to bridge the gap, ultimately to realize its untapped potential. Simulations in virtual source mode indicated enhanced beam brightness and a reduced beam half-angle with an increase the extraction voltage, promising up to tenfold times higher beam brightness compared with the crossover mode. The energy distribution measured using a prelens retarding field energy analyzer revealed an energy distribution of 0.55 eV and a high angular current density of 33 mA/sr in the virtual source mode. Therefore, the virtual source mode of LaB6 can provide a narrow energy distribution akin to that of a ZrO/W Schottky electron gun (1600 K) while having an angular current density over 2,000 times higher. In addition, the stability of the virtual source mode is ±0.022%, while that of the crossover mode is ±0.138%.

A critical review of adsorption isotherm models for aqueous contaminants: Curve characteristics, site energy distribution and common controversies.

The quantitative description of the equilibrium data by the isotherm models is an indispensable link in adsorption studies. The previous review papers focus on the underlying assumptions, fitting methods, error functions and practical applications of the isotherm models, usually ignoring their curve characteristics, selection criteria and common controversies. The main contents of this review include: (i) effect of the model parameters on the isotherm curves; (ii) determination of the site energy distribution; (iii) selection criteria of the isotherm models; and (iv) elimination of some common controversies. It is of great significance to reveal the curve characteristics for selecting a proper isotherm model. The site energy distribution is conducive to understanding the physicochemical properties of the adsorbent surface. The complete isotherm is recommended to be correlated with the experimental data. The model parameter qmax should be cautiously adopted for comparison of the adsorbent performance. The residual plot can be used to diagnose the fitting quality of the isotherm models further. This review also addresses some common mistakes and controversies and thereby avoids their propagation in future publications.

Studies on competitive adsorption characteristics of bisphenol A and 17α-ethinylestradiol on thermoplastic polyurethane by site energy distribution theory.

Compound pollution of microplastics and estrogens is a growing ecotoxicological problem in aquatic environments. The adsorption isothermal properties of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) on polyamide (TPU) in monosolute and bisolute systems were studied. Under the same adsorption concentration (1-4 mg L-1), EE2 had a greater adsorption capacity than BPA in the monsolute system. Compared to the energy distribution features of the adsorption sites of EE2 and BPA, the BPA adsorption sites were located in the higher energy area and were more evenly distributed than those of EE2, while the quantity of BPA adsorption sites was less than that of EE2. In the bisolute system, the average site energy, site energy inhomogeneity, and adsorption site numbers of BPA increased by 1.674, -17.166, and 16.793%, respectively. In comparison, the average site energy, site energy inhomogeneity, and adsorption sites numbers of EE2 increased by 2.267, 4.416, and 8.585%, respectively. The results showed that BPA and EE2 had a cooperative effect on the competitive adsorption of TPU. XPS analysis showed that BPA and EE2 had electron transfer on TPU, although the chemisorption effects and hydrogen bonds between BPA and TPU were more significant. Comparing the changes in the relative functional group content of TPU in monosolute and bisolute systems, BPA and EE2 were synergistically absorbed on TPU. This study can provide a theoretical reference for the study of competitive adsorption between coexisting organic pollutants.

Discussion on Electron Temperature of Gas-Discharge Plasma with Non-Maxwellian Electron Energy Distribution Function Based on Entropy and Statistical Physics.

Electron temperature is reconsidered for weakly-ionized oxygen and nitrogen plasmas with its discharge pressure of a few hundred Pa, with its electron density of the order of 1017m-3 and in a state of non-equilibrium, based on thermodynamics and statistical physics. The relationship between entropy and electron mean energy is focused on based on the electron energy distribution function (EEDF) calculated with the integro-differential Boltzmann equation for a given reduced electric field E/N. When the Boltzmann equation is solved, chemical kinetic equations are also simultaneously solved to determine essential excited species for the oxygen plasma, while vibrationally excited populations are solved for the nitrogen plasma, since the EEDF should be self-consistently found with the densities of collision counterparts of electrons. Next, the electron mean energy U and entropy S are calculated with the self-consistent EEDF obtained, where the entropy is calculated with the Gibbs's formula. Then, the "statistical" electron temperature Test is calculated as Test=[∂S/∂U]-1. The difference between Test and the electron kinetic temperature Tekin is discussed, which is defined as [2/(3k)] times of the mean electron energy U=⟨ϵ⟩, as well as the temperature given as a slope of the EEDF for each value of E/N from the viewpoint of statistical physics as well as of elementary processes in the oxygen or nitrogen plasma.

Energy mapping of the genetic code and genomic domains: implications for code evolution and molecular Darwinism.

When the iconic DNA genetic code is expressed in terms of energy differentials, one observes that information embedded in chemical sequences, including some biological outcomes, correlate with distinctive free energy profiles. Specifically, we find correlations between codon usage and codon free energy, suggestive of a thermodynamic selection for codon usage. We also find correlations between what are considered ancient amino acids and high codon free energy values. Such correlations may be reflective of the sequence-based genetic code fundamentally mapping as an energy code. In such a perspective, one can envision the genetic code as composed of interlocking thermodynamic cycles that allow codons to 'evolve' from each other through a series of sequential transitions and transversions, which are influenced by an energy landscape modulated by both thermodynamic and kinetic factors. As such, early evolution of the genetic code may have been driven, in part, by differential energetics, as opposed exclusively by the functionality of any gene product. In such a scenario, evolutionary pressures can, in part, derive from the optimization of biophysical properties (e.g. relative stabilities and relative rates), in addition to the classic perspective of being driven by a phenotypical adaptive advantage (natural selection). Such differential energy mapping of the genetic code, as well as larger genomic domains, may reflect an energetically resolved and evolved genomic landscape, consistent with a type of differential, energy-driven 'molecular Darwinism'. It should not be surprising that evolution of the code was influenced by differential energetics, as thermodynamics is the most general and universal branch of science that operates over all time and length scales.

High-Performance Compact Pre-Lens Retarding Field Energy Analyzer for Energy Distribution Measurements of an Electron Gun.

The energy distribution of an electron gun is one of the most important characteristics determining the performance of electron beam-based instruments, such as electron microscopes and electron energy loss spectroscopes. For accurate measurements of the energy distribution, this study presents a novel retarding field energy analyzer (RFEA) with the feature of an additional integrated pre-lens, which enables an adjustment of beam trajectory into the analyzer. The advantages of this analyzer are its compact size and simple electrode configuration. According to trajectory simulation theories, the optimum condition arises when the incident electron beam inside the RFEA is focused on the center of a retarding electrode. Comparing I­V curves depending on whether the pre-lens working or not, it is confirmed that the use of the pre-lens dramatically improves the energy resolution and efficiency of the signal acquisition process. The pre-lens RFEA was applied to characterize a Schottky electron gun under various temperatures and extraction voltages as operational conditions. When the tip temperature was increased by 50 K, we were able to measure an energy distribution broadening of 13.8 meV with the proposed pre-lens RFEA. The relative standard deviation of energy distribution was 0.7% for each working condition.

Development of a Noninvasive Real-Time Ion Energy Distribution Monitoring System Applicable to Collisional Plasma Sheath.

As the importance of ion-assisted surface processing based on low-temperature plasma increases, the monitoring of ion energy impinging into wafer surfaces becomes important. Monitoring methods that are noninvasive, real-time, and comprise ion collision in the sheath have received much research attention. However, in spite of this fact, most research was performed in invasive, not real-time, and collisionless ion sheath conditions. In this paper, we develop a noninvasive real-time IED monitoring system based on an ion trajectory simulation where the Monte Carlo collision method and an electrical model are adopted to describe collisions in sheaths. We technically, theoretically, and experimentally investigate the IED measurement with the proposed method, and compared it with the result of IEDs measured via a quadrupole mass spectrometer under various conditions. The comparison results show that there was no major change in the IEDs as radio-frequency power increased or the IED gradually became broad as gas pressure increased, which was in a good agreement with the results of the mass spectrometer.

Dissection of the Multichannel Reaction O(3P) + C2H2: Differential Cross-Sections and Product Energy Distributions.

The O(3P) + C2H2 reaction plays an important role in hydrocarbon combustion. It has two primary competing channels: H + HCCO (ketenyl) and CO + CH2 (triplet methylene). To further understand the microscopic dynamic mechanism of this reaction, we report here a detailed quasi-classical trajectory study of the O(3P) + C2H2 reaction on the recently developed full-dimensional potential energy surface (PES). The entrance barrier TS1 is the rate-limiting barrier in the reaction. The translation of reactants can greatly promote reactivity, due to strong coupling with the reaction coordinate at TS1. The O(3P) + C2H2 reaction progress through a complex-forming mechanism, in which the intermediate HCCHO lives at least through the duration of a rotational period. The energy redistribution takes place during the creation of the long-lived high vibrationally (and rotationally) excited HCCHO in the reaction. The product energy partitioning of the two channels and CO vibrational distributions agree with experimental data, and the vibrational state distributions of all modes of products present a Boltzmann-like distribution.

Low false positive and accurate detection of yeast cell viability and concentration using an automatic staining and lensfree imaging platform.

Yeast cell viability and concentration are the crucial factors affecting product quality in food industry and bio-fuel production, as well as the evaluation basis for environmental toxic compounds. To overcome the drawbacks of existing methods, including high error, false positive and low automation, we propose a highly accurate approach based on an automatic staining and high-throughput lensfree imaging platform. A precisely controlled staining process is implemented automatically, which largely avoids the error caused by inappropriate exposure times. Based on optical simulation analysis, energy distribution characteristics are proposed. They are better with steady theoretical evidence for live yeast cell recognition. The parameters are directly extracted from raw cell fingerprints without any reconstruction. Those progresses improve robustness and increase efficiency. Availability of this approach is validated by compared the detection results with gold-standard PI counting method in a H2O2 toxicity test. So it is expected to be widely used in industrial production and environmental toxicity assessment.

Energetics of blood flow in Fontan circulation under VAD support.

The need to simulate the normal operating conditions of the human body is the key factor in every study and engineering process of bioelectronic devices designed for implantation. The Fontan procedure is an example of such a process aimed to support the human body function. It is a standard treatment method for patients with a functionally univentricular heart. However, it has significant drawbacks such as overload of the only functional heart ventricle that often leads to the necessity of the heart transplantation. In this study, we analyze the total cavopulmonary connection (TCPC) influence on the blood with and without connected auxiliary blood circulation pump. We investigate four different types of TCPC configurations, analyze blood pressure and different flow rate, study the turbulent kinetic energy distribution, and evaluate hydraulic and power losses for various cases. Finally, we calculate volumetric scalar shear stresses distribution and demonstrate the high potential of TCPC configuration with connected rotary pump as a tool for the load redistribution in the functional heart ventricle. This work is particularly relevant for improving existing TCPCs' quality that can extend the life of Fontan patients. Moreover, it also applies to the reduction of morbidity and mortality of the patients waiting for the heart transplantation.

Monte Carlo investigation of electron specific energy distribution in a single cell model.

Knowledge of microdosimetric quantities of certain radionuclides is important in radio immune cancer therapies. Specific energy distribution of radionuclides, which are bound to the cell, is the microdosimetric quantity essential in the process of radionuclide selection for patient tumour treatment. The aim of this paper is to establish an applicable method to determine microdosimetric quantities for various radionuclides. The established method is based on knowledge of microdosimetric quantities of monoenergetic electrons. In this paper these quantities are determined for the single-cell model for a range of electron energies up to [Formula: see text], using the Monte Carlo transport code PENELOPE. The results show that using monoenergetic specific energies, reconstruction of the specific energy of beta-emitting radionuclides can be successfully done with very high accuracy. Microdosimetric quantities share information about the physical processes involved and give insight about energy depositions, which is of use in the procedure of radionuclide selection for a given type of therapy.

Adsorption of dissolved organic matter (DOM) on polystyrene microplastics in aquatic environments: Kinetic, isotherm and site energy distribution analysis.

Microplastics and dissolved organic matter (DOM) are ubiquitous in aquatic environments. The adsorption behavior of DOM on microplastics in aquatic environments is a prominent concern. In this study, the adsorption of two types of DOM, Suwannee River Humic Acid (HA) and Suwannee River Fulvic Acid (FA), on polystyrene microplastics (PSMPs, 10 µm) in aquatic environments was investigated. The adsorption of both HA and FA on PSMPs could be well described by using pseudo second-order and Freundlich models. The adsorption of HA and FA on PSMPs was low pH-dependent, particularly for FA adsorption. However, the elevated ionic strength slightly increased the adsorption of HA and FA on PSMPs. Based on Freundlich model, the site energy distribution of HA and FA adsorption on PSMPs under the experimental conditions were estimated. HA and FA first occupied the high-energy adsorption sites and then diffused to the low-energy adsorption sites on PSMPs. With higher site energies, HA demonstrated a much stronger adsorption affinity to PSMPs than FA. The adsorption site heterogeneity (σe*) on PSMPs under the experimental conditions were close. Hydrophobic interaction and π-π electron donor acceptor interaction acted simultaneously in the HA and FA adsorption on PSMPs. The results of this study suggested that the environmental behaviors of microplastics would be influenced by the amount and the type of DOM as well as solution chemistry.