The Properties of Water in the Pressure–Temperature Landscape

Water represents the major component of most food systems. During thermal or high-pressure processing, physical and chemical properties of water are changed. The p–T diagram represents an obvious presentation of isoproperty lines and their pressure and temperature dependencies. In this work, 15 different properties of pure water are shown as isoproperty lines in the pressure–temperature landscape. By using functional relationships from the “International Association for the Properties of Water and Steam” and databases from the “National Institute of Standards and Technology,” highest accuracy is guaranteed. Applying the generated graphs, a compact overview is given and a wide range of thermal and high-pressure processes can easily be compared. The different pressure and temperature dependencies of all properties showed the complexity of medium conditions during thermal and high-pressure processing. An extended understanding of pressure–temperature dependencies will improve process concepts as well as industrial applications at high temperature and high isostatic pressure.     

A “parallel plate” electrostatic model for bimolecular rate constants applied to electron transfer proteins

A “parallel plate” model describing the electrostatic potential energy of protein-protein interactions is presented that provides an analytical representation of the effect of ionic strength on a bimolecular rate constant. The model takes into account the asymmetric distribution of charge on the surface of the protein and localized charges at the site of electron transfer that are modeled as elements of a parallel plate condenser. Both monopolar and dipolar interactions are included. Examples of simple (monophasic) and complex (biphasic) ionic strength dependencies obtained from experiments with several electron transfer protein systems are presented, all of which can be accommodated by the model. The simple cases do not require the use of both monopolar and dipolar terms (i.e., they can be fit well by either alone). The biphasic dependencies can be fit only by using dipolar and monopolar terms of opposite sign, which is physically unreasonable for the molecules considered. Alternatively, the high ionic strength portion of the complex dependencies can be fit using either the monopolar term alone or the complete equation; this assumes a model in which such behavior is a consequence of electron transfer mechanisms involving changes in orientation or site of reaction as the ionic strength is varied. Based on these analyses, we conclude that the principal applications of the model presented here are to provide information about the structural properties of intermediate electron transfer complexes and to quantify comparisons between related proteins or site-specific mutants. We also conclude that the relative contributions of monopolar and dipolar effects to protein electron transfer kinetics cannot be evaluated from experimental data by present approximations.     

The study of the role of the water medium in the mechanism of action of peptides in low and ultra low doses

The correlation between the structures and conformations of short peptides KE, EW, AEDG and other, their influence on the dynamic properties of water and dose/biologic effect dependencies in a wide range of concentrations were regarded. Their effects on the dynamic properties of water were studied by temperature dependencies (5-45 degrees C) of infrared spectra of the solutions in the near (5180 cm-1) and far (200 cm-1). In vitro biotesting included the determination of the proliferative activity of thymocytes, a bimodal curve with the second maximum were detected at super-low doses (10(-17)-10(-15) mol/l). Authors propose a hypothesis that for superlow concentrations the formation and distance transmission of a signal from ligand to a target cell without the formation of any ligand-receptor complex take place. An active role in this model belongs to water medium acting according to the solution mechanism.     

The unfolding of our understanding of RNA structure: a personal reflection

In this article, I review how our research on RNA began, how it led us to demonstrate the single-stranded nature of RNA, and the ways in which it differs from double-stranded DNA. It was based on the development of a method for the isolation of undegraded rRNA and the observation that in rRNA preparations due to their viscosity behavior resemble a flexible, contractile coil. In support of this assumption, birefringence of flow measurements showed that rRNA solutions gave moderate positive values, which disappeared upon addition of salt. This is in contrast with DNA solutions where considerable negative birefringence persists even in the presence of salt. Further studies on RNA showed a close correlation of the ionic strength dependencies of optical rotation, optical density and hydrodynamic properties. These early results indicated that rRNA and tRNA possess a significant secondary structure. I then review the basis of the hairpin model for the secondary structure of RNA and finally, summarize current understanding of the tertiary structure of RNA.     

Birefringence of tropomyosin crystals.

The birefringence of tropomyosin crystals was measured in the temperature range 5 degrees-35 degrees C. The experimental results are compared with a simple model calculation based on the theory developed by Wiener for the optical properties of colloidal systems. The difference between experimental and theoretical values is less than 15%, which denotes a good agreement given the simplicity of the model. A value of 0.011 was obtained for the intrinsic birefringence of the tropomyosin molecule. The temperature dependence of the crystal birefringence could be accounted for in part by a change of the unit cell parameters; this change was experimentally observed by others in x-ray diffraction experiments.     

Complex sequencing rules of birdsong can be explained by simple hidden Markov processes

Complex sequencing rules observed in birdsongs provide an opportunity to investigate the neural mechanism for generating complex sequential behaviors. To relate the findings from studying birdsongs to other sequential behaviors such as human speech and musical performance, it is crucial to characterize the statistical properties of the sequencing rules in birdsongs. However, the properties of the sequencing rules in birdsongs have not yet been fully addressed. In this study, we investigate the statistical properties of the complex birdsong of the Bengalese finch (Lonchura striata var. domestica). Based on manual-annotated syllable labeles, we first show that there are significant higher-order context dependencies in Bengalese finch songs, that is, which syllable appears next depends on more than one previous syllable. We then analyze acoustic features of the song and show that higher-order context dependencies can be explained using first-order hidden state transition dynamics with redundant hidden states. This model corresponds to hidden Markov models (HMMs), well known statistical models with a large range of application for time series modeling. The song annotation with these models with first-order hidden state dynamics agreed well with manual annotation, the score was comparable to that of a second-order HMM, and surpassed the zeroth-order model (the Gaussian mixture model; GMM), which does not use context information. Our results imply that the hierarchical representation with hidden state dynamics may underlie the neural implementation for generating complex behavioral sequences with higher-order dependencies.     

Temperature dependence of leaf-level CO2 fixation: revising biochemical coefficients through analysis of leaf three-dimensional structure

CO2 fixation in a leaf is determined by biochemical and physical processes within the boundaries set by leaf structure. Traditionally determined temperature dependencies of biochemical processes include physical processes related to CO2 exchange that result in inaccurate estimates of parameter values. A realistic three-dimensional model of a birch (Betula pendula) leaf was used to distinguish between the physical and biochemical processes affecting the temperature dependence of CO2 exchange, to determine new chloroplastic temperature dependencies for V c(max) and Jmax based on experiments, and to analyse mesophyll diffusion in detail. The constraint created by dissolution of CO2 at cell surfaces substantially decreased the CO2 flux and its concentration inside chloroplasts, especially at high temperatures. Consequently, newly determined chloroplastic V c(max) and Jmax were more temperature dependent than originally. The role of carbonic anhydrase in mesophyll diffusion appeared to be minor under representative mid-day nonwater-limited conditions. Leaf structure and physical processes significantly affect the apparent temperature dependence of CO2 exchange, especially at optimal high temperatures when the photosynthetic sink is strong. The influence of three-dimensional leaf structure on the light environment inside a leaf is marked and affects the local choice between Jmax and V c(max)-limited assimilation rates.     

Ultrasonic study of melittin effects on phospholipid model membranes.

Low dose effects of melittin on dilute suspensions of dipalmitoylphosphatidylcholine multilamellar vesicles are investigated by studying the acoustic properties of the system. The temperature dependencies of sound velocity and absorption have been measured at 7.2 MHz in the temperature range of 20-55 degrees C, for different peptide/lipid molar ratios, R. The most pronounced effects were observed at R = 5 x 10(-3), in the vicinity of the pretransition, with a simultaneous increase in sound absorption and velocity. This indicates that melittin affects the polar head group region of the bilayer resulting in a decrease in mobility of the polar head groups. A nonmonotonic dependence of the main transition temperature, with an initial decrease followed by an increase as melittin is added, is interpreted as a consequence of a destabilizing action of the interfaces between mellitin-affected clusters and the unaffected phase.     

Mechanism of Nonlinear Photoinduced Anisotropy in Bacteriorhodopsin and its Derivatives

Polymer films made with photosensitive chromophore protein bacteriorhodopsin (BR) from the extreme halophile Halobacterium salinarium as well as films made with BR derivatives exhibit a nonlinear photoinduced anisotropy. Two different methods can be used to induce anisotropy in polymer BR films. The first method is based on the anisotropic properties of the initial form of the photocycle, BR570 (B-type anisotropy). Another method is based on the anisotropic properties of the longest-lived photocycle intermediate M412 (M-type anisotropy). CW gas lasers were employed to induce a reversible anisotropy in polymer BR films. Nonlinear photoinduced anisotropy is discussed in the context of a model for the anisotropic photoselection of BR molecules under linearly polarized light. A comparison of the experimental dependencies of nonlinear photoinduced anisotropy on laser intensity with similar calculated dependencies enables one to determine the molecular dichroism of BR and its derivatives not only for the initial form of the photocycle, B but also for the longest-lived intermediate M. Here we present the data showing the correlation between the laser induced nonlinear anisotropic properties and chromophore/protein interactions in BR. The effect of polymer binder on the nonlinear photoanisotropic properties of polymer BR films is also described.     

Hidden smectic properties of a chiral side-chain co-oligomer

We recently showed that a side-chain industrial co-oligosiloxane presents a quenchable enlarged blue phase behaviour at the cholesteric-isotropic phase transition. In this paper, we present the results of a structural study based on X-ray diffraction, differential scanning calorimetry and optical measurements. In particular, the smectic A organisation is demonstrated in the lower temperature domain, which was hitherto understood as a cholesteric phase. A structural model for this phase is proposed on the basis of the analysis of the anisotropic scattering of stretched fibers. Our results also suggest that the observed glass transition is indeed a rather complex phenomenon, which seems to involve not only the freezing of the main chains, but also smectic correlations at the side-chain level. Moreover, the calorimetric study indicates that, notwithstanding the conservation of the processed film's optical properties, low kinetic reorganisations occur at room temperature.     

Simulation of the propagation effects in the HF-EPR spectra of non-diluted magnetic materials

The high field EPR spectra of non-diluted magnetic material are affected by propagation effects when the wavelength of the exciting radiation is of the same order of magnitude of the optical path within the sample. Beyond the optical path, the shape of the spectra is determined by the dielectric constant and by the magnetization of the material and through these quantities it depends on the temperature. A detailed knowledge of the physical properties of the material is therefore mandatory for a complete study of the phenomenon. In order to demonstrate the propagation effect, the 285 GHz EPR spectra of tetramethyl-ammonium manganese chloride (TMMC) were recorded as a function of temperature and a simulation of the spectra was performed on the basis of a simplified model of the propagation of far infrared radiation around the resonance field. The universality of the effect was illustrated by measuring other magnetic materials such as ferrite.     

Quantitative patterns of the thermal inactivation of microorganisms as a basis for obtaining high-quality vaccinal preparations

The model of the thermal inactivation of microorganisms is presented. This model permits the explanation of all existing kinetic dependencies relating to the death of microorganisms, the restoration of sublethal damages, the influence of the medium and the temperature of incubation on the process of the production and control of vaccinal preparations.     

Suspended Particulate Matter detection in the North Sea by hyper spectral airborne remote sensing

A spectral model is developed describing the relation between optical spectral reflectance and sampled suspended particulate matter concentration. This reflectance model is based on inherent optical properties of North Sea colouring water constituents. Hyper spectral airborne observations by a CASI scanner are carried out in the Dutch coastal zone and interpreted making use of the reflectance model. A non linear relation between reflectance and suspended particulate matter concentration is found. Variability of sampled suspended matter concentration is high, in contrast to this the variability of interpreted spectral measurements is much lower. Abbreviations: IOP – inherent optical properties; CASI – compact airborne spectral imager; SPM – suspended particulate matter; CHL – chlorophyll; FWHM – full width half maximum; r.m.s – root mean square.     

A numerical model of birch pollen emission and dispersion in the atmosphere. Description of the emission module

A birch pollen emission model is described and its main features are discussed. The development of the model is based on a double-threshold temperature sum model that describes the propagation of the flowering season and naturally links to the thermal time models to predict the onset and duration of flowering. For the flowering season, the emission model considers ambient humidity and precipitation rate, both of which suppress the pollen release, as well as wind speed and turbulence intensity, which promote it. These dependencies are qualitatively evaluated using the aerobiological observations. Reflecting the probabilistic character of the flowering of an individual tree in a population, the model introduces relaxation functions at the start and end of the season. The physical basis of the suggested birch pollen emission model is compared with another comprehensive emission module reported in literature. The emission model has been implemented in the SILAM dispersion modelling system, the results of which are evaluated in a companion paper.     

Polyelectrolyte precipitation of proteins: II. Models of the particle size distributions

A population-balance model has been used to characterize continuous polyelectrolyte precipitation of egg white proteins. We have modeled the particle size distributions of aggregates formed under a range of mixing conditions. The models, accounting for aggregate growth (by both shear-driven and Brownian-like collisions), breakage (by hydrodynamic shear or aggregate-aggregate collisions), and birth (by the breakage of large aggregates), fit the data well. The kinetic constants show dependencies on shear rate and residence time that have not been previously theoretically predicted; these dependencies are due in part to aging effects on the aggregate. The model constants show a dominance of growth over breakage, supporting qualitative interpretations of the particle size distributions. A mechanism for growth-rate enhancement, caused by polymer extensions from the particle surfaces, produced improved model performance. A collisional breakage mechanism is supported.     

Temperature-dependent optical rotatory dispersion properties of helical muscle proteins and homopolymers

Thermally induced helix–coil transitions of myosin rod, light meromyosin, and tropomyosin were studied by optical rotatory dispersion (ORD). Fractional helicity was calculated from both the Moffitt-Yang parameter, b₀, and the corrected mean residue rotation [m′] at 231.4 nm. Between 3 and 30°C, [m′] increases linearly with a slope of 59/°C, whereas b₀ is virtually constant, indicating apparently different thermal melting behavior. Poly(L -lysine) and poly(L -glutamic acid) in their helical forms and myoglobin also show a nearly linear temperature dependence of [m′]_231.4. Muscle proteins in 6M guanidine hydrochloride and the random-coil forms of the homopolymers exhibit temperature-dependent values of [m′]_231.4 and b₀. We conclude from these observations that ORD properties of both α-helices and random-coil polypeptides have significant intrinsic temperature dependencies. A new method of estimating fractional helicity as a function of temperature is proposed.     

Effects of low temperature on respiration and uptake of rubidium ions by excised barley and corn roots

The effect of temperature upon ion uptake and respiration was investigated with excised roots of corn (Zea mays) and barley (Hordeum vulgare). A strong inhibition (Q₁₀ = 5 to 8) of ion uptake was observed at temperatures below 10 C. At higher temperatures more normal temperature dependencies (Q₁₀ = 1.3 to 2) were obtained. When the data were plotted according to the Arrhenius relationship, two different activation energies were indicated above and below 10 C. Other studies have related such changes with temperature in activation energy of processes to changes in membrane properties induced by temperature. These results suggest that such phase transitions may affect ion uptake processes. If so, then differences among species in their capacity to maintain normal root function at low soil temperature and to resist low temperature stress may be related to differences in the physical properties of cellular membranes.     

The global-scale temperature and moisture dependencies of soil organic carbon decomposition: an analysis using a mechanistic decomposition model

Since the decomposition rate of soil organic carbon (SOC) varies as a function of environmental conditions, global climate change is expected to alter SOC decomposition dynamics, and the resulting changes in the amount of CO₂ emitted from soils will feedback onto the rate at which climate change occurs. While this soil feedback is expected to be significant because the amount of SOC is substantially more than the amount of carbon in the atmosphere, the environmental dependencies of decomposition at global scales that determine the magnitude of the soil feedback have remained poorly characterized. In this study, we address this issue by fitting a mechanistic decomposition model to a global dataset of SOC, optimizing the model’s temperature and moisture dependencies to best match the observed global distribution of SOC. The results of the analysis indicate that the temperature sensitivity of decomposition at global scales (Q ₁₀=1.37) is significantly less than is assumed by many terrestrial ecosystem models that directly apply temperature sensitivity from small-scale studies, and that the maximal rate of decomposition occurs at higher moisture values than is assumed by many models. These findings imply that the magnitude of the soil decomposition feedback onto rate of global climate change will be less sensitive to increases in temperature, and modeling of temperature and moisture dependencies of SOC decomposition in global-scale models should consider effects of scale.     

Computersimulation der Trocknung biologischer Produkte

The extend of non-enzymatic browning and ascorbic acid loss during air drying of a slab are predicted by computer, utilizing moisture and temperature dependencies of reaction kinetics together with simulated data for either averaged moisture contents. Results show that the extend of quality loss is a function of the drying parameters. The computer model is useful for the optimization of quality retention during dehydration of biotechnological products and foods.