On the modulation effect of pulsing and static magnetic fields and mechanical vibrations on barley seed hydration

The changes of wet and dry weights of barley seed in different periods of swelling were studied in seeds treated with Extremely Low Frequency Electromagnetic Fields (ELF EMF), Static Magnetic Fields (SMF) and Mechanical Vibrations (MV) in cold (4 degrees C) and warm (20 degrees C) distilled water as well as in seeds non-treated (control). The metabolic dependent seed hydration, dry weight loss and water binding in seed were modulated by preliminary EMF, SMF and MV-induced treatment of distilled water. The specific electrical conductivity (SEC) of control and treated distilled water was measured before the seed incubation. Frequency and intensity "windows" (i.e. range of frequency or intensity) for the effect of EMF, MV and SMF (correspondingly) on seed hydration, solubility and water binding in seed were studied. These "windows" were different in various phases of seed swelling. It is suggested that water structure modification is the result of valence angle changes (SMF and EMF) and dipole molecules vibration (EMF and MV) has different effects on the process of hydration, solubility and water binding in seed. These results are important from the point of understanding the mechanisms of the biological effect of EMF, as well as from the point of agriculture.     

The biological effect of extremely low frequency electromagnetic fields and vibrations on barley seed hydration and germination

The changes of wet and dry weights and germination of barley seed in different periods of its swelling in nontreated (control), extremely low frequency electromagnetic fields (ELF EMF) )-treated, and extremely low frequency vibrations (ELFV)-treated cold (4 degrees C) and warm (20 degrees C) distilled water (DW) were studied. The metabolic-dependent seed hydration, dry weight dissolving, germination, and water binding in seed were modulated by preliminary EMF- and ELFV-treated DW. Frequency "windows" for the effect of EMF and ELFV on seed hydration, solubility, water binding in seed, and germination were discovered. These "windows" were different for EMF and ELFV, as well as in various phases of seed swelling. It is suggested that EMF-induced water structure modification has a different biological effect on the process of seed hydration, solubility, water binding in seed, and germination compared to ELFV.     

Lipid participation in intracellular freezing avoidance mechanisms of lettuce seed

Freeze-fracture electron microscopy was used to study water content related freezing resistance in Grand Rapids lettuce seeds. Consistent and recognizable conformational changes occurred in lipid-water phases of lettuce seeds at different moisture contents. In air-dry lettuce seed cotyledons, the lipids lying in spherical lipid bodies near the cell wall appeared amorphous, while the structure was crystalline above 20% water content. The lipid bodies interassociated into membrane bilayers in seeds containing 20 to 25% water. Such lyotropic phase transitions in membrane lipids during lettuce seed hydration are believed to contribute to the biphasic freezing behavior observed in lettuce seeds at different moisture contents and to provide a natural freezing tolerance mechanism for highly desiccated plant tissues such as seeds.     

The physiology of seed hydration and dehydration, and the relation between water stress and the control of germination: a review

Abstract Current interest in seed hydration treatments for the improvement of level, rate and uniformity of germination or field emergence has revealed how little is known of the physiology of germination control under water stress. This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration. Inhibition of germination, though not of seed activation, at certain levels of water stress is likened to various forms of dormancy, and the mechanism governing the initiation of cell elongation is suggested as the possible key to control over germination. Several lines of evidence on cell membrane integrity and action, and their responses to external factors, point to the role that the membrane may play in cell elongation (and hence germination) control, and membrane integrity may also be associated with the transition between seed deterioration at one hydration level and seed activation and repair at slightly higher hydration levels. Seed activation without germination is also considered in an ecological context.     

NMR study of seed hydration with deuterated water: dependence of proton signals on hydration level.

Proton NMR signals in seeds are shown to depend on hydration level. In fact at low water amount, as it occurs in many native seeds, protons can have a restricted mobility and are not detectable. A NMR method for measuring the dependence of proton signals on hydration is reported. The method also allows the separation of the contributions of water and non-water protons in a low-resolution NMR experiment. It is based on successive hydrations (with deuterated water) - desiccation steps and on the analysis of the transverse magnetization decay curves.     

Effect of seed moisture content and d‐limonene on oviposition decisions of the seed beetle Callosobruchus maculatus

Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae) is a cosmopolitan pest of stored pulses and legumes. Under legume storage conditions neither adults nor larvae drink, with larvae obtaining their hydration from metabolic water. However, lack of water limits female fecundity and longevity, thus females might be expected to preferentially oviposit on seeds with high moisture content so as to minimize water stress on their offspring. This was tested by offering females a choice of seeds that differed in relation to their level of water content. After controlling for differences in seed size, females were found to preferentially oviposit on the driest seeds. Offspring size and larval survival were equivalent on seeds that differed in moisture content, which in combination with the preference to lay on the driest seeds would indicate that the egg laying decisions of C. maculatus females do not function to minimize larval water stress. Analysis of the chemical volatiles released by seeds that differed in their moisture content revealed a greater level of d ‐limonene in the environment surrounding high moisture seeds. d ‐limonene has known anti‐herbivory properties, thus we suggest the observed female preference for dry seeds may be related to the observed difference in the level of d ‐limonene in the immediate vicinity of beans that differ with respect to their moisture content.     

Hydration dynamics of the collagen triple helix by NMR

The hydration of the collagen-like Ac-(Gly-Pro-Hyp)(6)-NH(2) triple-helical peptide in solution was investigated using an integrated set of high-resolution NMR hydration experiments, including different recently developed exchange-network editing methods. This approach was designed to explore the hydration dynamics in the proximity of labile groups, such as the hydroxyproline hydroxyl group, and revealed that the first shell of hydration in collagen-like triple helices is kinetically labile with upper limits for water molecule residence times in the nanosecond to sub-nanosecond range. This result is consistent with a "hopping" hydration model in which solvent molecules are exchanged in and out of solvation sites at a rate that is not directly correlated to the degree of site localization. The hopping model thus reconciles the dynamic view of hydration revealed by NMR with the previously suggested partially ordered semi-clathrate-like cylinder of hydration. In addition, the nanosecond to sub-nanosecond upper limits for water molecule residence times imply that hydration-dehydration events are not likely to be the rate-limiting step for triple helix self-recognition, complementing previous investigations on water dynamics in collagen fibers. This study has also revealed labile proton features expected to facilitate the characterization of the structure and folding of triple helices in collagen peptides.     

Use of low temperature sem to locate free water in frozen,hydrated seed tissues of Glycine max (Leguminosae)

Low temperature field emission electron microscopy was used to determine the location of free water in soybean seeds. Frozen, hydrated soybean seeds were fractured, the water etched from the fractured surface, and then part of the etched surface was refractured. The resulting surface, which contained a freeze-fractured face as well as a freeze-etched face was coated with platinum and viewed on the cryostage of a low temperature field emission electron microscope. Two surfaces could be viewed simultaneously to determine the location of water in the seed tissue. Viewing the fractured surface gave an indication of the extent of hydration of the tissue. Viewing the etched surface detailed the macro- and microanatomy of the tissue. Viewing the intersection between the fractured and etched surfaces allowed observation of the environment of partially etched cells and organelles. The technique avoids artifacts associated with chemical fixation, dehydration, and critical-point drying, procedures that affect the water content of the seed. The technique does not affect the degree of hydration of the seed and can be used to localize water in the inter- and intracellular environment of the seed. This technique could find wide application in studies of water relationships of seeds during development, maturation, and imbibition.     

Supercooling ability in apple seeds as affected by temperature-induced modifications in water relations in the seed parts

Prolonged storage of apple fruits ( Pyrus malus L. cv. Golden Delicious) at different temperatures (0, 12 and 35°C) decreased the water content in seed coats and endosperms, higher temperatures being much more effective than the lower (0°C) one. No effect of the temperature on the embryo hydration was found. However, a pronounced decrease in water potential in the embryos was observed during the first 9 weeks. The decrease was much faster and the water potential reached lower levels in embryos isolated from seeds pretreated with higher temperatures (12 or 35°C) than from cold-pretreated (0°C) material. Higher temperatures of fruit storage also resulted in a decreased permeability of the embryo membranes to electrolytes and sugars. At the same time, membrane permeability to water was not modified. It is proposed that the previously observed occurrence of the discontinuous type of freezing in apple seeds (Nguyen and Kacperska, Physiologia Plantarum (X): 000-000, 1989) is associated with the temperature-induced dehydration of seed coat and endosperm, whereas a higher super cooling ability of the high-temperature-pretreated embryos is due to a decrease in the free energy of water in the system, and to the effective protection of embryo cells against heterogenous ice nucleation. The changes in water potential showed a high negative correlation with the embryo phospholipid content determined in the other work (Nguyen et al. Plant Physiol. Bio chem. 25: 697–703, 1987). Therefore, it is proposed that changes in matrix potential play an important role in the regulation of the water potential in the embryo cells.     

Water/polymer interactions in a poly(amidoamine) hydrogel studied by NMR spectroscopy

Samples of PAAH1, a cross-linked polymer belonging to the family of poly(amidoamine)s, were investigated at different hydration levels by means of 13C and 1H NMR techniques in order to obtain information on water/polymer interactions. Carbonyl oxygens and amine nitrogens were identified as the main sites of interaction giving hydrogen bonding with water molecules. The polymer turned out to be uniformly plasticized already at moderate degrees of swelling. The hydration process was found to occur in a stepwise manner, with the first batch of water saturating a hydration layer and additional water filling the polymer meshes. The proportion of water in the different states was quantitatively determined.     

Monte Carlo simulation of hydration of the nucleic acid fragments

Systems containing a base or a base pair and 25 water molecules, as well as a helical stack and 30 water molecules per base pair, have been simulated. Changes in the base hydration shell structure, after the bases have been included into the pair and then into the base pair stack, are discussed. Hydration shells of several configurations of the base pair stacks are discussed. Probabilities of formation of the hydrogen-bonded bridges of 1, 2 and 3 water molecules between hydrophilic centres have been estimated. The hydration shell structure was shown to depend on the nature of the base pair and on the stack configuration, while dependence of the global hydration shell characteristics on the stack configuration has been proved to be rather slight. The most typical structural elements of hydration shells, in the glycosidic (minor in B-like conformation) and non-glycosidic (major) grooves, for different configurations of AU and GC stacks, have been found and discussed. The number of hydrogen bonds between water molecules and bases per water molecule was shown to change upon transformation of the stack from A to B configuration. This result is discussed in connection with the reasons for B to A conformational transition and the concept of "water economy". Hydration shell patterns of NH2-groups of AU and GC helical stacks differ significantly.     

Influence of water clustering on the dynamics of hydration water at the surface of a lysozyme

Dynamics of hydration water at the surface of a lysozyme molecule is studied by computer simulations at various hydration levels in relation with water clustering and percolation transition. Increase of the translational mobility of water molecules at the surface of a rigid lysozyme molecule upon hydration is governed by the water-water interactions. Lysozyme dynamics strongly affect translational motions of water and this dynamic coupling is maximal at hydration levels, corresponding to the formation of a spanning water network. Anomalous diffusion of hydration water does not depend on hydration level up to monolayer coverage and reflects spatial disorder. Rotational dynamics of water molecules show stretched exponential decay at low hydrations. With increasing hydration, we observe appearance of weakly bound water molecules with bulklike rotational dynamics, whose fraction achieves 20-25% at the percolation threshold.     

Role of flexibility and polarity as determinants of the hydration of internal cavities and pockets in proteins

Molecular dynamics simulations of Staphylococcal nuclease and of 10 variants with internal polar or ionizable groups were performed to investigate systematically the molecular determinants of hydration of internal cavities and pockets in proteins. In contrast to apolar cavities in rigid carbon structures, such as nanotubes or buckeyballs, internal cavities in proteins that are large enough to house a few water molecules will most likely be dehydrated unless they contain a source of polarity. The water content in the protein interior can be modulated by the flexibility of protein elements that interact with water, which can impart positional disorder to water molecules, or bias the pattern of internal hydration that is stabilized. This might explain differences in the patterns of hydration observed in crystal structures obtained at cryogenic and room temperature conditions. The ability of molecular dynamics simulations to determine the most likely sites of water binding in internal pockets and cavities depends on its efficiency in sampling the hydration of internal sites and alternative protein and water conformations. This can be enhanced significantly by performing multiple molecular dynamics simulations as well as simulations started from different initial hydration states.     

Difference in the hydration water mobility around F-actin and myosin subfragment-1 studied by quasielastic neutron scattering

Hydration water is essential for a protein to perform its biological function properly. In this study, the dynamics of hydration water around F-actin and myosin subfragment-1 (S1), which are the partner proteins playing a major role in various cellular functions related to cell motility including muscle contraction, was characterized by incoherent quasielastic neutron scattering (QENS). The QENS measurements on the D₂O- and H₂O-solution samples of F-actin and S1 provided the spectra of hydration water, from which the translational diffusion coefficient (D_T), the residence time (τ_T), and the rotational correlation time (τ_R) were evaluated. The D_T value of the hydration water of S1 was found to be much smaller than that of the hydration water of F-actin while the τ_T values were similar between S1 and F-actin. On the other hand, the τ_R values of the hydration water of S1 was found to be larger than that of the hydration water of F-actin. It was also found that the D_T and τ_R values of the hydration water of F-actin are similar to those of bulk water. These results suggest a significant difference in mobility of the hydration water between S1 and F-actin: S1 has the typical hydration water, the mobility of which is reduced compared with that of bulk water, while F-actin has the unique hydration water, the mobility of which is close to that of bulk water rather than the typical hydration water around proteins.     

Large-scale networks of hydration water molecules around bovine beta-trypsin revealed by cryogenic X-ray crystal structure analysis.

The hydration structure of bovine beta-trypsin was investigated in cryogenic X-ray diffraction experiments. Three crystal forms of the enzyme inhibited by benzamidine with different molecular packing were selected to deduce the hydration structure for the entire surface of the enzyme. The crystal structures in all three of the crystal forms were refined at the resolution of 1.8 A at 100 K and 293 K. The number of hydration water molecules around the enzyme at 100 K was 1.5 to two times larger than that at 293 K, indicating that the motion of hydration water was quenched by cooling. In particular, the increase in the number of hydration water molecules was prominent on flat and electrostatically neutral surface areas. The water-to-protein mass ratio and the radius of gyration of a structural model of hydrated trypsin at 100 K was consistent with the results obtained by other experimental techniques for proteins in solution. Hydration water molecules formed aggregates of various shapes and dimensions, and some of the aggregates even covered hydrophobic residues by forming oligomeric arrangements. In addition, the aggregates brought about large-scale networks of hydrogen bonds. The networks covered a large proportion of the surface of trypsin like a patchwork, and mechanically linked several secondary structures of the enzyme. By merging the hydration structures of the three crystal forms at 100 K, a distribution function of hydration water molecules was introduced to approximate the static hydration structure of trypsin in solution. The function showed that the negatively charged active site of trypsin tended to be easily exposed to bulk solvent. This result is of interest with respect to the solvent shielding effect and the recognition of a positively charged substrate by trypsin.     

The mechanism of the type III antifreeze protein action: a computational study

The random network model of water quantitatively describes the different hydration heat capacities of polar and apolar solutes in terms of differential distortions of the water-water hydrogen bonding angle in the first hydration shell. This method of hydration analysis is applied here to study the hydration of the wild type III thermal hysteresis protein from eel pout and three mutations at residue 16. Wild type and one mutant have full activity, the other two mutants have little or no anti-freeze (thermal hysteresis) activity. The analysis reveals significant differences in the hydration structure of the ice-binding site (centered on residue 16) among four proteins. For the A16T and A16Y mutants with reduced activity, polar groups have a typical polar-like hydration. For the wild type and mutant A16C with 100% of the wild type activity, polar groups have unusual, very apolar-like hydration. In the latter case, hydrating water molecules form a more ice-like pattern of hydrogen bonding on the ice-binding face, while in the former case water-water H-bonds are more distorted and more heterogenous. Overall, the binding surface of active protein strongly enhances the water tetrahedral structure, i.e. promotes ice-like hydration. It is concluded that the specific shape, residue size and clustering of both polar/apolar groups are essential for the binding surface to recognize, and preferentially interact with nascent ice crystals forming in liquid water.     

Modeling hydration mechanisms of enzymes in nonpolar and polar organic solvents

A comprehensive study of the hydration mechanism of an enzyme in nonaqueous media was done using molecular dynamics simulations in five organic solvents with different polarities, namely, hexane, 3-pentanone, diisopropyl ether, ethanol, and acetonitrile. In these solvents, the serine protease cutinase from Fusarium solani pisi was increasingly hydrated with 12 different hydration levels ranging from 5% to 100% (w/w) (weight of water/weight of protein). The ability of organic solvents to 'strip off' water from the enzyme surface was clearly dependent on the nature of the organic solvent. The rmsd of the enzyme from the crystal structure was shown to be lower at specific hydration levels, depending on the organic solvent used. It was also shown that organic solvents determine the structure and dynamics of water at the enzyme surface. Nonpolar solvents enhance the formation of large clusters of water that are tightly bound to the enzyme, whereas water in polar organic solvents is fragmented in small clusters loosely bound to the enzyme surface. Ions seem to play an important role in the stabilization of exposed charged residues, mainly at low hydration levels. A common feature is found for the preferential localization of water molecules at particular regions of the enzyme surface in all organic solvents: water seems to be localized at equivalent regions of the enzyme surface independently of the organic solvent employed.     

Hydration parameters defining the structural-functional status of tissues containing collagen

By the method of SHF-dielectrometry there was studied hydration of collagens isolated from different frog tissues of related species. Hydration was shown to be tissue-specific, i.e. the quantity of hydrate water in collagen 1 isolated from different animals being constant.     

Prolonged aerated hydration for improvement of seed quality in Brassica oleracea L.

Seeds of cauliflower cv. Hipop and Brussels sprouts cv. Asmer Aries were aged at 20% moisture content for 24 h; all seeds retained a germination of over 70% after ageing although the mean germination time increased. Prolonged aerated hydration for up to 32 h at 20°C followed drying resulted in improved performance of both unaged and aged cauliflower seeds and aged Brussels sprouts. Thus, all seed showed reductions in the mean germination time to the extent that after 32 h hydration the aged cauliflower seeds performed as well as high quality unaged seed. The improvement of aged seeds was also revealed an increase in germination after the controlled deterioration test following up to 24 h (cauliflower) or 32 h (Brussels sprouts) aerated hydration. This increase was indicative of a decrease in the extent of deterioration present after aerated hydration. Deleterious effects of prolonged hydration were observed in Brussels sprouts after 32 h although these may be explained desiccation injury after treatment since radicle emergence had occurred during hydration. The improvements in seed performance may be explained the activation of metabolic repair occurring during the early part of the hydration period therereducing the extent of deterioration that has been sustained during ageing, with further improvements due to the advancement of the germination process.     

Hydration of Escherichia coli lipids. Deuterium T1 relaxation time studies of phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine

The hydration properties of Escherichia coli lipids (phosphatidylglycerol, phosphatidylethanolamine) and synthetic 1,2-dioleoyl-sn-glycero-3-phosphocholine in H2O/2H2O mixtures (9:1, v/v) were investigated with 2H-NMR. Comparison of the 2H2O spin lattice relaxation time (T1) as a function of the water content revealed a remarkable quantitative similarity of all three lipid-H2O systems. Two distinct hydration regions could be discerned in the T1 relaxation time profile. (1) A minimum of 11-16 water molecules was needed to form a primary hydration shell, characterized by an average relaxation time of T1 approximately equal to 90 ms. (2) Additional water was found to be in exchange with the primary hydration shell. The exchange process could be described in terms of a two-site exchange model, assuming rapid exchange between bulk water with T1 = 500 ms and hydration water with T1 = 80-120 ms. Analysis of the linewidth and the residual quadrupole splitting (at low water content) confirmed the size of the primary hydration layer. However, each lipid-water system exhibited a somewhat different linewidth behavior, and a detailed molecular interpretation appeared to be preposterous.