Fourier transform infrared microspectroscopy detects changes in protein secondary structure associated with desiccation tolerance in developing maize embryos

Protecting Proteins from Desiccation Stress Using Molecular Glasses and Gels

Faced with desiccation stress, many organisms deploy strategies to maintain the integrity of their cellular components. Amorphous glassy media composed of small molecular solutes or protein gels present general strategies for protecting against drying. We review these strategies and the proposed molecular mechanisms to explain protein protection in a vitreous matrix under conditions of low hydration. We also describe efforts to exploit similar strategies in technological applications for protecting proteins in dry or highly desiccated states. Finally, we outline open questions and possibilities for future explorations.

Effects of Altitudinal Gradient on Physicochemical and Rheological Potential of Quinoa Cultivars

The protein, carbohydrate, and fat characteristics of quinoa grains reflect in their techno-functional potential. This aspect has been little studied in quinoa, while some physicochemical and rheological characteristics have been generalized for all cultivars under all primary production conditions. The aim of this research is to determine the agro-industrial potential of different quinoa cultivars evaluated under different environments through physicochemical and rheological responses. This study has a factorial design with a first level corresponding to cultivars and a second level to production zones. The results showed that the cultivars present high compositional variability. It was also found that the altitudinal gradient changes protein and starch composition, protein secondary structure, and starch structural conformation. In addition, significant variations were found in viscosity, breakdown, and dispersion setback for all treatments. However, there were no differences between treatments before heating/cooling and after heat treatment.

Root cell wall chemistry remodelling enhanced arsenic fixation of a cabbage cultivar

The low- and high-arsenic (As) transferring cultivars (LTC and HTC) of cabbage showed significant differences in As uptake and distribution. We hypothesise that chemistry of root cell wall matrix plays a critical role. LTC and HTC were treated with As and grown for 60 days. As concentration and distribution at subcellular and cell wall component (pectin, hemicellulose and lignin) levels were determined. Remodelling enzymes (PME and PAL) and functional groups of cell wall were analysed. Results showed that shoot biomass of LTC was not affected by As. Less As was accumulated in shoot of LTC than HTC. LTC allocated more As in root and majority of As was deposited in cell wall. LTC had more hemicellulose 1 (HC1) and lignin, PME and PAL activities. The uronic acid contents of pectin, HC1 or HC2 were all positively (P < 0.05) correlated with As concentrations in each component, respectively. Chemistry of LTC root cell wall was remodelled in terms of changes in porosity, HC and lignin contents, and functional groups, which potentially exerted coupling effects on As entering and deposition. The LTC can restrain As in roots through changing characteristics of root cell wall matrix.

Structural Characterization and Antioxidant Capacity of Quinoa Cultivars Using Techniques of FT-MIR and UHPLC/ESI-Orbitrap MS Spectroscopy

The existence of more of 16,000 varieties of quinoa accessions around the world has caused a disregard on their structural and phytochemical characteristics. Most of such accessions belong to cultivars settled in Colombia. The goal of this research was to evaluate the structural attributes and antioxidant capacities from six quinoa cultivars with high productive potential from central regions in Colombia. This study used middle-range infrared spectroscopy (IR-MIR) to determine the proteins, starch and lipids distinctive to quinoa grains. Ultra-high-performance liquid chromatography electrospray ionization Orbitrap, along with high-resolution mass spectrometry (UHPLC/ESI-Orbitrap MS), were also used to identify the existence of polyphenols in cultivars. The antioxidant capacity was determined through DPPH, ABTS and FRAP. The spectrums exhibited significant variances on the transmittance bands associated with 2922 cm-1, 1016 cm-1 and 1633 cm-1. Moreover, the intensity variations on the peaks from the secondary protein structure were identified, mainly on the bands associated with β-Sheet-1 and -2, random coil α elice and β-turns-2 and -3. Changes found in the ratios 996 cm-1/1014 cm-1 and 1041 cm-1/1014 cm-1 were associated with the crystalline/amorphous affinity. Regarding the antioxidant capacity, great differences were identified (p < 0.001) mainly through FRAP methods, while the phenolic acids and flavonoids were determined by UHPLC/ESI-Orbitrap MS techniques. The presence of apigenin and pinocembrin on grains was reported for the first time. Titicaca and Nariño were the most phytochemically diverse quinoa seeds.

Geochemistry and the Origin of Life: From Extraterrestrial Processes, Chemical Evolution on Earth, Fossilized Life's Records, to Natures of the Extant Life

In 2001, the first author (S.N.) led the publication of a book entitled "Geochemistry and the origin of life" in collaboration with Dr. Andre Brack aiming to figure out geo- and astro-chemical processes essential for the emergence of life. Since then, a great number of research progress has been achieved in the relevant topics from our group and others, ranging from the extraterrestrial inputs of life's building blocks, the chemical evolution on Earth with the aid of mineral catalysts, to the fossilized records of ancient microorganisms. Here, in addition to summarizing these findings for the origin and early evolution of life, we propose a new hypothesis for the generation and co-evolution of photosynthesis with the redox and photochemical conditions on the Earth's surface. Besides these bottom-up approaches, we introduce an experimental study on the role of water molecules in the life's function, focusing on the transition from live, dormant, and dead states through dehydration/hydration. Further spectroscopic studies on the hydrogen bonding behaviors of water molecules in living cells will provide important clues to solve the complex nature of life.

Investigation of the magnetic field effect upon interpolymeric complexes formation based on bovine serum albumin and poly(aspartic acid)

The study presents a novel strategy for obtaining highly ordered interpolymeric complexes based on a protein, bovine serum albumin and a synthetic polymer, poly(aspartic acid). In this approach, experimental tests were carried out in the presence of a magnetic field of different intensities, namely 0.11 T and 0.3 T produced by permanent magnets. The influence of the magnetic force on the complexation process and the resulted self-assembled structures were studied by means of FTIR spectroscopy, X-ray diffraction, DLS, SEM microscopy and in vitro assay. The changes in the FTIR spectra acquired after 24 h of exposure were connected with conformational changes in the secondary structure and increased interactions between polymers, particularly when a higher intensity field was used. Due to a large anisotropy of magnetic susceptibility characteristic to both proteins and polypeptides, the magnetic field generated ordered assemblies consisting in globular structures of nanometric dimensions. This assembly strategy using magnets, along with remote manipulation capability can provide a versatile, contact-free, and inexpensive tool to create new, complex materials with tailorable characteristics.

Chemical profile, energy values, and protein molecular structure characteristics of biofuel/bio-oil co-products (carinata meal) in comparison with canola meal

To our knowledge, little information exists on nutritive values and molecular structural characteristics associated with protein biopolymers of carinata meal from biofuel and bio-oil processing. The objectives of this study were to investigate (1) chemical compositions; (2) protein and carbohydrate subfractions partitioned by the Cornell Net Carbohydrate and Protein System (CNCPS); (3) truly digestible nutrients and energy values; (4) protein conformation spectral characteristics using the ATR-FT/IR technique; and (5) the correlation between protein intrinsic structural features and nutrient profiles of carinata meal in comparison with conventional canola meal as references. The results showed that carinata meal was higher (p < 0.05) in soluble crude protein (SCP, 55.6% CP) and nonprotein nitrogen (NPN, 38.5% CP) and lower in acid detergent insoluble crude protein (ADICP, 1.3% CP) compared to canola meal. Although no differences were found in CP and carbohydrate (CHO) contents, CNCPS protein and carbohydrate subfractions were different (p < 0.05) between carinata meal and canola meal. Carinata meal has similar contents of total digestible nutrient (TDN) and predicted energy values to canoal meal (p > 0.05). As for protein spectral features, much greater IR absorbance in amide I height and area as well as α-helix and β-sheet height for carinata meal by 20-31% (p < 0.05) was found compared with canola meal; however, results from agglomerative hierarchical cluster analysis (CLA) and principal component analysis (PCA) indicated these two meals could not be distinguished completely within the protein spectrum (ca. 1728-1478 cm(-1)). Additionally, close correlations were observed between protein structural parameters and protein nutrient profiles and subfractions. All the comparisons between carinata meal and canola meal in our study indicated that carinata meal could be used as a potential high-protein supplement source for ruminants. Further study is needed on more information associated with nutrient degradability, utilization, and availability of carinata meal to ruminants for its better and effective application in animal industry.

Microprobing the molecular spatial distribution and structural architecture of feed-type sorghum seed tissue (Sorghum Bicolor L.) using the synchrotron radiation infrared microspectroscopy technique

Sorghum seed (Sorghum bicolor L.) has unique degradation and fermentation behaviours compared with other cereal grains such as wheat, barley and corn. This may be related to its cell and cell-wall architecture. The advanced synchrotron radiation infrared microspectroscopy (SR-IMS) technique enables the study of cell or living cell biochemistry within cellular dimensions. The objective of this study was to use the SR-IMS imaging technique to microprobe molecular spatial distribution and cell architecture of the sorghum seed tissue comprehensively. High-density mapping was carried out using SR-IMS on beamline U2B at the National Synchrotron Light Source (Brookhaven National Laboratory, NY, USA). Molecular images were systematically recorded from the outside to the inside of the seed tissue under various chemical functional groups and their ratios [peaks at ∼1725 (carbonyl C=O ester), 1650 (amide I), 1657 (protein secondary structure α-helix), 1628 (protein secondary structure β-sheet), 1550 (amide II), 1515 (aromatic compounds of lignin), 1428, 1371, 1245 (cellulosic compounds in plant seed tissue), 1025 (non-structural CHO, starch granules), 1246 (cellulosic material), 1160 (CHO), 1150 (CHO), 1080 (CHO), 930 (CHO), 860 (CHO), 3350 (OH and NH stretching), 2960 (CH(3) anti-symmetric), 2929 (CH(2) anti-symmetric), 2877 (CH(3) symmetric) and 2848 cm(-1) (CH(2) asymmetric)]. The relative protein secondary structure α-helix to β-sheet ratio image, protein amide I to starch granule ratio image, and anti-symmetric CH(3) to CH(2) ratio image were also investigated within the intact sorghum seed tissue. The results showed unique cell architecture, and the molecular spatial distribution and intensity in the sorghum seed tissue (which were analyzed through microprobe molecular imaging) were generated using SR-IMS. This imaging technique and methodology has high potential and could be used for scientists to develop specific cereal grain varieties with targeted food and feed quality, and can also be used to monitor the degree of grain maturity, grain damage, the fate of organic contaminants and the effect of chemical treatment on plant and grain seeds.

Molecular basis of protein structure in proanthocyanidin and anthocyanin-enhanced Lc-transgenic alfalfa in relation to nutritive value using synchrotron-radiation FTIR microspectroscopy: a novel approach

To date there has been very little application of synchrotron radiation-based Fourier transform infrared microspectroscopy (SRFTIRM) to the study of molecular structures in plant forage in relation to livestock digestive behavior and nutrient availability. Protein inherent structure, among other factors such as protein matrix, affects nutritive quality, fermentation and degradation behavior in both humans and animals. The relative percentage of protein secondary structure influences protein value. A high percentage of beta-sheets usually reduce the access of gastrointestinal digestive enzymes to the protein. Reduced accessibility results in poor digestibility and as a result, low protein value. The objective of this study was to use SRFTIRM to compare protein molecular structure of alfalfa plant tissues transformed with the maize Lc regulatory gene with non-transgenic alfalfa protein within cellular and subcellular dimensions and to quantify protein inherent structure profiles using Gaussian and Lorentzian methods of multi-component peak modeling. Protein molecular structure revealed by this method included alpha-helices, beta-sheets and other structures such as beta-turns and random coils. Hierarchical cluster analysis and principal component analysis of the synchrotron data, as well as accurate spectral analysis based on curve fitting, showed that transgenic alfalfa contained a relatively lower (P<0.05) percentage of the model-fitted alpha-helices (29 vs. 34) and model-fitted beta-sheets (22 vs. 27) and a higher (P<0.05) percentage of other model-fitted structures (49 vs. 39). Transgenic alfalfa protein displayed no difference (P>0.05) in the ratio of alpha-helices to beta-sheets (average: 1.4) and higher (P<0.05) ratios of alpha-helices to others (0.7 vs. 0.9) and beta-sheets to others (0.5 vs. 0.8) than the non-transgenic alfalfa protein. The transgenic protein structures also exhibited no difference (P>0.05) in the vibrational intensity of protein amide I (average of 24) and amide II areas (average of 10) and their ratio (average of 2.4) compared with non-transgenic alfalfa. Cluster analysis and principal component analysis showed no significant differences between the two genotypes in the broad molecular fingerprint region, amides I and II regions, and the carbohydrate molecular region, indicating they are highly related to each other. The results suggest that transgenic Lc-alfalfa leaves contain similar proteins to non-transgenic alfalfa (because amide I and II intensities were identical), but a subtle difference in protein molecular structure after freeze drying. Further study is needed to understand the relationship between these structural profiles and biological features such as protein nutrient availability, protein bypass and digestive behavior of livestock fed with this type of forage.

Use of Fourier Transform Infrared (FTIR) spectroscopy to study cadmium-induced changes in Padina tetrastromatica (Hauck)

The aim of this study is to adopt the approach of metabolic fingerprinting through the use of Fourier Transform Infrared (FTIR) technique to understand changes in the chemical structure in Padina tetrastromatica (Hauck). The marine brown alga under study was grown in two different environmental conditions; in natural seawater (P. tetrastromatica (c)) and in seawater suplemented with 50 ppm of cadmium (P. tetrastromatica (t)) for a three-week period in the laboratory. The second derivative, IR specrum in the mid-infrared region (4000-400 cm(-1)) was used for discriminating and identifying various functional groups present in P. tetrastromatica (c). On exposure to Cd, P. tetrastromatica (t) accumulated 412 ppm of Cd and showed perturbation in the band structure in the mid-IR absorption region. Variation in spectral features of the IR bands of P. tetrastromatica (untreated and treated) suggests that cadmium ions bind to hydroxyl, amino, carbonyl and phosphoryl functionalities. This was attributable to the presence of the following specific bands. A band at 3666 cm(-1) in untreated P. tetrastromatica (c) while a band at 3560 cm(-1) in Cd-treated P. tetrastromatica (t) due to non bonded and bonded O-H respectively. Similarly, non bonded N-H for P. tetrastromatica (c) showed two bands at 3500 cm(-1) and 3450 cm(-1) due to the N-H stretching vibrations and a band at 1577 cm(-1) due to N-H bending vibrations, while an intense band at 3350 cm(-1) due to bonded N-H stretching vibrations and at 1571 cm(-1) due to bending vibrations was observed for Cd-treated P. tetrastromatica (t). Involvement of ester carbonyl group is characterized by the presence of a band at 1764 cm(-1) in untreated P. tetrastromatica (c) while the Cd-treated P. tetrastromatica (t) showed the band at 1760 cm(-1). The intensity of the band at 1710 cm(-1) in the control samples decreased drastically after cadmium treatment indicating carbonyl of COOH to be involved in metal chelation. A band at 1224 cm(-1) for untreated P. tetrastromatica (c) and at 1220 cm(-1) for Cd-treated P. tetrastromatica (t) is indicative of the involvement of phosphoryl group in metal binding. Several other such changes were also evident and discussed in this paper. Based on our observation, FTIR technique proves to be an efficient tool for detecting structural changes and probable binding sites induced by the presence of a metal pollutant, cadmium, in the marine environment.

Use of Fourier Transform Infrared (FTIR) Spectroscopy to Study Cadmium-Induced Changes in Padina Tetrastromatica (Hauck)

The aim of this study is to adopt the approach of metabolic fingerprinting through the use of Fourier Transform Infrared (FTIR) technique to understand changes in the chemical structure in Padina tetrastromatica (Hauck). The marine brown alga under study was grown in two different environmental conditions; in natural seawater ( P. tetrastromatica (c)) and in seawater suplemented with 50 ppm of cadmium ( P. tetrastromatica (t)) for a three-week period in the laboratory. The second derivative, IR specrum in the mid-infrared region (4000-400 cm-1) was used for discriminating and identifying various functional groups present in P. tetrastromatica (c). On exposure to Cd, P. tetrastromatica (t) accumulated 412 ppm of Cd and showed perturbation in the band structure in the mid-IR absorption region. Variation in spectral features of the IR bands of P. tetrastromatica (untreated and treated) suggests that cadmium ions bind to hydroxyl, amino, carbonyl and phosphoryl functionalities. This was attributable to the presence of the following specific bands. A band at 3666 cm-1 in untreated P. tetrastromatica (c) while a band at 3560 cm-1 in Cd-treated P. tetrastromatica (t) due to non bonded and bonded O-H respectively. Similarly, non bonded N-H for P. tetrastromatica (c) showed two bands at 3500 cm-1 and 3450 cm-1 due to the N-H stretching vibrations and a band at 1577cm-1 due to N-H bending vibrations, while an intense band at 3350 cm-1 due to bonded N-H stretching vibrations and at 1571 cm-1 due to bending vibrations was observed for Cd-treated P. tetrastromatica (t). Involvement of ester carbonyl group is characterized by the presence of a band at 1764 cm-1 in untreated P. tetrastromatica (c) while the Cd-treated P. tetrastromatica (t) showed the band at 1760 cm-1. The intensity of the band at 1710 cm-1 in the control samples decreased drastically after cadmium treatment indicating carbonyl of COOH to be involved in metal chelation. A band at 1224 cm-1 for untreated P. tetrastromatica ( c) and at 1220 cm-1 for Cd-treated P. tetrastromatica (t) is indicative of the involvement of phosphoryl group in metal binding. Several other such changes were also evident and discussed in this paper. Based on our observation, FTIR technique proves to be an efficient tool for detecting structural changes and probable binding sites induced by the presence of a metal pollutant, cadmium, in the marine environment.

Molecular chemical structure of barley proteins revealed by ultra-spatially resolved synchrotron light sourced FTIR microspectroscopy: comparison of barley varieties

Barley protein structure affects the barley quality, fermentation, and degradation behavior in both humans and animals among other factors such as protein matrix. Publications show various biological differences among barley varieties such as Valier and Harrington, which have significantly different degradation behaviors. The objectives of this study were to reveal the molecular structure of barley protein, comparing various varieties (Dolly, Valier, Harrington, LP955, AC Metcalfe, and Sisler), and quantify protein structure profiles using Gaussian and Lorentzian methods of multi-component peak modeling by using the ultra-spatially resolved synchrotron light sourced Fourier transform infrared microspectroscopy (SFTIRM). The items of the protein molecular structure revealed included protein structure alpha-helices, beta-sheets, and others such as beta-turns and random coils. The experiment was performed at the National Synchrotron Light Source in Brookhaven National Laboratory (BNL, US Department of Energy, NY). The results showed that with the SFTIRM, the molecular structure of barley protein could be revealed. Barley protein structures exhibited significant differences among the varieties in terms of proportion and ratio of model-fitted alpha-helices, beta-sheets, and others. By using multi-component peaks modeling at protein amide I region of 1710-1576 cm-1, the results show that barley protein consisted of approximately 18-34% of alpha-helices, 14-25% of beta-sheets, and 44-69% others. AC Metcalfe, Sisler, and LP955 consisted of higher (P<0.05) proportions of alpha-helices (30-34%) than Dolly and Valier (alpha-helices 18-23%). Harrington was in between which was 25%. For protein beta-sheets, AC Metcalfe, and LP955 consisted of higher proportions (22-25%) than Dolly and Valier (13-17%). Different barley varieties contained different alpha-helix to beta-sheet ratios, ranging from 1.4 to 2.0, although the difference were insignificant (P>0.05). The ratio of alpha-helices to others (0.3 to 1.0, P<0.05) and that of beta-sheets to others (0.2 to 0.8, P<0.05) were different among the barley varieties. It needs to be pointed out that using a multi-peak modeling for protein structure analysis is only for making relative estimates and not exact determinations and only for the comparison purpose between varieties. The principal component analysis showed that protein amide I Fourier self-deconvolution spectra were different among the barley varieties, indicating that protein internal molecular structure differed. The above results demonstrate the potential of the SFTIRM to localize relatively pure protein areas in barley tissues and reveal protein molecular structure. The results indicated relative differences in protein structures among the barley varieties, which may partly explain the biological differences among the barley varieties. Further study is needed to understand the relationship between barley molecular chemical structure and biological features in terms of nutrient availability and digestive behavior.

The effect of fructan on membrane lipid organization and dynamics in the dry state

Fructans are a group of fructose-based oligo- and polysaccharides, which appear to be involved in membrane preservation during dehydration by interacting with the membrane lipids. To get further understanding of the protective mechanism, the consequences of the fructan-membrane lipid interaction for the molecular organization and dynamics in the dry state were studied. POPC and DMPC were investigated in the dry state by (2)H, (31)P NMR, and Fourier transform infrared spectroscopy using two types of fructan and dextran. The order-disorder transition temperature of dry POPC was reduced by 70 degrees C in the presence of fructan. Fructan increased the mobility of the acyl chains, but immobilized the lipid headgroup region. Most likely, fructans insert between the headgroups of lipids, thereby spacing the acyl chains. This results in a much lower phase transition temperature. The headgroup is immobilized by the interaction with fructan. The location of the interaction with the lipid headgroup is different for the inulin-type fructan compared to the levan-type fructan, since inulin shows interaction with the lipid phosphate group, whereas levan does not. Dextran did not influence the phase transition temperature of dry POPC showing that reduction of this temperature is not a general property of polysaccharides.

Desiccation tolerance of spermatozoa dried at ambient temperature: production of fetal mice

Long-term preservation of mouse sperm by desiccation is economically and logistically attractive. The current investigation is a feasibility study of the preservation of mouse sperm by convective drying in an inert gas (nitrogen). Mouse sperm from the B6D2F1 strain isolated in an EGTA-supplemented Tris-HCl buffer were dried using three different drying rates and were stored for 18-24 h at 4 degrees C. The mean final moisture content was <5% for all the protocols. After intracytoplasmic sperm injection (ICSI), the mean blastocyst formation rates were 64%, 58%, and 35% using the rapid-, moderate-, and slow-drying protocols, respectively. The slow-drying protocol resulted in a rate of development significantly lower than that observed using rapid- and moderate-drying protocols and indicated that a slower drying rate may be detrimental to the DNA integrity of mouse sperm. The transfer of 85 two- or four-cell embryos that were produced using rapidly desiccated sperm resulted in 11 fetuses (13%) on Day 15 compared with the production of 34 fetuses (40%) produced using the transfer of 86 two- or four-cell embryos that were produced using fresh sperm (P < 0.05). The results demonstrate the feasibility of using a convective drying protocol for the successful desiccation of mouse sperm and identifies some of the important parameters required for optimization of the procedure.

Conformation of a group 2 late embryogenesis abundant protein from soybean. Evidence of poly (L-proline)-type II structure

Late embryogenesis abundant (LEA) proteins are members of a large group of hydrophilic, glycine-rich proteins found in plants, algae, fungi, and bacteria known collectively as hydrophilins that are preferentially expressed in response to dehydration or hyperosmotic stress. Group 2 LEA (dehydrins or responsive to abscisic acid) proteins are postulated to stabilize macromolecules against damage by freezing, dehydration, ionic, or osmotic stress. However, the structural and physicochemical properties of group 2 LEA proteins that account for such functions remain unknown. We have analyzed the structural properties of a recombinant form of a soybean (Glycine max) group 2 LEA (rGmDHN1). Differential scanning calorimetry of purified rGmDHN1 demonstrated that the protein does not display a cooperative unfolding transition upon heating. Ultraviolet absorption and circular dichroism spectroscopy revealed that the protein is in a largely hydrated and unstructured conformation in solution. However, ultraviolet absorption and circular dichroism measurements collected at different temperatures showed that the protein exists in equilibrium between two extended conformational states: unordered and left-handed extended helical or poly (L-proline)-type II structures. It is estimated that 27% of the residues of rGmDHN1 adopt or poly (L-proline)-type II-like helical conformation at 12 degrees C. The content of extended helix gradually decreases to 15% as the temperature is increased to 80 degrees C. Studies of the conformation of the protein in solution in the presence of liposomes, trifluoroethanol, and sodium dodecyl sulfate indicated that rGmDHN1 has a very low intrinsic ability to adopt alpha-helical structure and to interact with phospholipid bilayers through amphipathic alpha-helices. The ability of the protein to remain in a highly extended conformation at low temperatures could constitute the basis of the functional role of GmDHN1 in the prevention of freezing, desiccation, ionic, or osmotic stress-related damage to macromolecular structures.

Early salt stress effects on the changes in chemical composition in leaves of ice plant and Arabidopsis. A Fourier transform infrared spectroscopy study

A technique based on Fourier transform infrared (FT-IR) spectrometry was developed to detect the corresponding changes in chemical composition associated with the rapid changes in sodium and water content in 200 mM NaCl-stressed halophyte ice plants (Mesembryanthemum crystallinum). The changes in glycophyte Arabidopsis stressed with 50 mM NaCl were also examined for comparison. The obtained IR spectra were further processed by deconvolution and curve fitting to examine the chemical nature of the responding sources in the leaves. Using three stages of ice plant leaves, absorption bands corresponding to carbohydrates, cell wall pectin, and proteins were identified, with distinct IR spectra representing each developmental stage. Within 48 h of mild salt stress, the absorption band intensities in the fingerprint region increased continuously in both plants, suggesting that the carbon assimilation was not affected at the early stage of stress. The intensities of ester and amide I absorption bands decreased slightly in Arabidopsis but increased in ice plant, suggesting that the cell expansion and protein synthesis ceased in Arabidopsis but continued in ice plant. In both plants, the shift in amide I absorption band was observed hourly after salt stress, indicating a rapid conformational change of cellular proteins. Analyses of the ratio between major and minor amide I absorption band revealed that ice plant was able to maintain a higher-ordered form of proteins under stress. Furthermore, the changes in protein conformation showed a positive correlation to the leaf sodium contents in ice plant, but not in Arabidopsis.

Expression profiling of reciprocal maize hybrids divergent for cold germination and desiccation tolerance

Recombinant inbred lines (RILs) derived from B73 x M017 were screened for cold germination (CG) and desiccation tolerance (DT) phenotypes. Reciprocal F(1) hybrids were made between divergent RILs, and hybrids that showed differential phenotypes (parent-of-origin effect) for CG or DT were selected for profiling mRNA and protein expression. mRNA and proteins were extracted from embryo axes of seed germinated for 11 d at 12.5 degrees C in the dark and developing embryos at 40% seed moisture (R5 stage) for CG and DT, respectively. GeneCalling analysis, an open-ended mRNA profiling method, identified 336 of 32,496 and 656 of 32,940 cDNA fragments that showed >or=1.5-fold change in expression between the reciprocal F(1) hybrids for CG and DT, respectively. Protein expression map (PEM) analysis, an open-ended two-dimensional polyacrylamide gel electrophoresis, identified 117 of 2,641 and 205 of 1,876 detected proteins to be differentially expressed with >or=1.5-fold change between the reciprocal F(1) hybrids in CG and DT samples, respectively. A subset of these proteins was identified by tandem mass spectrometry followed by database query of the spectra. The differentially expressed genes/proteins were classified into various functional groups including carbohydrate and amino acid metabolism, ion transporters, stress and defense response, polyamine metabolism, chaperonins, cytoskeleton associated, etc. Phenotypic analysis of seed from self-pollinated ears of the reciprocal F(1) hybrids displayed small differences compared with the reciprocal hybrids themselves, suggesting a negligible effect of cytoplasmic factors on CG and DT traits. The results provide leads to improving our understanding of the genes involved in stress response during seed maturation and germination.

Non-disaccharide-based mechanisms of protection during drying

Few tissues or organisms can survive the removal of nearly all their intra and extracellular water. These few have developed specialized adaptations to protect their cellular components from the damage caused by desiccation and rehydration. One mechanism, common to almost all such organisms, is the accumulation of disaccharides within cells and tissues at the onset of dehydration. This adaptation has been extensively studied and will not be considered in this review. It has become increasingly clear that true desiccation tolerance is likely to involve several mechanisms working in concert; thus, we will highlight several other important and complimentary adaptations found especially in the dehydration-resistant tissues of higher plants. These include the scavenging of reactive oxygen species, the down-regulation of metabolism, and the accumulation of certain amphiphilic solutes, proteins, and polysaccharides.

Isolation and characterization of a D-7 LEA protein from pollen that stabilizes glasses in vitro

A heat-soluble protein present in substantial quantities in Typha latifolia pollen was purified to homogeneity. The protein was subjected to cyanogen bromide cleavage, and the peptides produced were separated by HPLC chromatography and sequenced. The two sequences determined were found to be related to the putative D76 LEA protein from Brassica napus seeds and one of them to the D-7 LEA protein from upland cotton. This suggests the pollen protein to be a member of the LEA group III family of proteins. The secondary structure of the protein in solution and in the dry state was investigated using Fourier transform IR spectroscopy. Whereas the protein in solution was highly unordered, being largely in a random coil conformation, the conformation was largely alpha-helical after fast drying. Slow drying reversibly led to both alpha-helical and intermolecular extended beta-sheet structures. When dried in the presence of sucrose, the protein adopted alpha-helical conformation, irrespective of drying rate. The effect of the protein on the stability of sucrose glasses was also investigated. The dehydrated mixture of sucrose and the LEA protein had higher glass transition temperatures and average strength of hydrogen bonding than dehydrated sucrose alone. We suggest that LEA proteins may play a role together with sugars in the formation of a tight hydrogen bonding network in the dehydrating cytoplasm, thus conferring long-term stability.

Changes in wheat germination following gamma-ray irradiation: an in vivo electronic paramagnetic resonance spin-probe study

Embryos excised from wheat (Triticum aestivum) grains following gamma-ray irradiation at different doses were analyzed on membrane permeability by electron paramagnetic resonance (EPR) technique with 4-oxo-2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPONE) as spin probe to acquire an EPR spectrum. The broadening agent ferricyanide added leads to changes in the high-field region of the EPR spectrum, which reflects differences in membrane permeability. R-value, defined as the ratio of water (W) to lipid (L) component in height in the high-field region of the EPR spectrum, symbolizes membrane permeability for a given sample. The R-values corresponding to a certain dose treatment of grains displayed a definitive distribution pattern. A unit row vector with 20 components was used to describe the R-value distribution pattern for a given treatment. The transaction angle between vectors corresponding to grains irradiated and unirradiated, &theta;, was used as quantitative index for membrane permeability changes following gamma-ray irradiation. gamma-Ray irradiated grains germinated at low rates, and the regression equation of germination rate as a function of the irradiation dose is: Germination Rate (%)=94.8 exp[-0.264xIrradiation Dose (kGy)] (r(2)=0.991, P<0.001). Embryos excised from grains following gamma-ray irradiation show increases in &theta; values with irradiation dose. The &theta; value is negatively linearly correlated with the germination rate. It suggests that gamma-ray irradiation leading to increases in membrane permeability is consistent with that leading to low germination rate of grains. The introduction to vector analysis method on membrane permeability changes in this study is very practical.

Changed properties of the cytoplasmic matrix associated with desiccation tolerance of dried carrot somatic embryos. An In situ fourier transform infrared spectroscopic study

Abscisic acid-pretreated carrot (Daucus carota) somatic embryos survive dehydration upon slow drying, but fast drying leads to poor survival of the embryos. To determine whether the acquisition of desiccation tolerance is associated with changes in the physical stability of the cytoplasm, in situ Fourier transform infrared microspectroscopy was used. Although protein denaturation temperatures were similar in the embryos after slow or fast drying, the extent of the denaturation was greater after fast drying. Slowly dried embryos are in a glassy state at room temperature, and no clearly defined glassy matrix was observed in the rapidly dried embryos. At room temperature the average strength of hydrogen bonding was much weaker in the rapidly dried than in the slowly dried embryos. We interpreted the molecular packing to be "less tight" in the rapidly dried embryos. Whereas sucrose (Suc) is the major soluble carbohydrate after fast drying, upon slow drying the trisaccharide umbelliferose accumulates at the expense of Suc. The possibly protective role of umbelliferose was tested on protein and phospholipid model systems, using Suc as a reference. Both umbelliferose and Suc form a stable glass with drying: They depress the transition temperature of dry liposomal membranes equally well, they both prevent leakage from dry liposomes after rehydration, and they protect a polypeptide that is desiccation sensitive. The similar protection properties in model systems and the apparent interchangeability of both sugars in viable, dry somatic embryos suggest no special role of umbelliferose in the improved physical stability of the slowly dried embryos. Also, during slow drying LEA (late-embryogenesis abundant) transcripts are expressed. We suggest that LEA proteins embedded in the glassy matrix confer stability to these slowly dried embryos.

Properties of proteins and the glassy matrix in maturation-defective mutant seeds of Arabidopsis thaliana

In situ Fourier transform infrared microspectroscopy was used to study the heat stability of proteins and hydrogen bonding interactions in dry maturation-defective mutant seeds of Arabidopsis thaliana. alpha-Helical, turn and beta-sheet conformations were the major protein secondary structures in all of these seeds. On heating, intermolecular extended beta-sheet structures, typical of protein denaturation, were formed in abscisic acid-insensitive (abi3) and leafy cotyledon (lec) mutant seeds. Proteins in dry wild-type seeds did not denature up to 150 degrees C, but those in dry desiccation-sensitive, lec1-1, lec1-3 and abi3-5 seeds did at 68, 89 and 87 degrees C, respectively. In the desiccation-tolerant abi3-7 and abi3-1 seeds, denaturation commenced above 120 and 135 degrees C, respectively. Seeds of the aba1-1 abi3-1 double mutant showed signs of denaturation already upon drying. The molecular packing in the seeds was studied by observing the shift in the position of the OH-stretching vibration band with temperature. The maximal rate of change of this band with temperature was much higher in the desiccation-sensitive abi3-5, aba1-1 abi3-1, lec1-1, and lec1-3 mutant seeds than in the desiccation-tolerant wild-type, abi3-1, abi3-7, and lec2-1 seeds. We interpret this to mean that the molecular packing density is higher in dry desiccation-tolerant than in dry desiccation-sensitive seeds, which is associated with a higher or lower protein denaturation temperature, respectively. The results are discussed in relation to the physiological and biochemical characteristics of these mutant seeds.

Dehydration-induced conformational changes of poly-L-lysine as influenced by drying rate and carbohydrates

The conformation of hydrated and air-dried poly-L-lysine in thin films was studied using Fourier transform IR spectroscopy in the amide-I region. Hydrated poly-L-lysine has a random coil conformation. Upon slow drying of small droplets of the polypeptide solution over a period of several hours, an extended beta-sheet conformation is adopted. This conformational transition can be prevented by fast air-drying within 2-3 min. Slow air-drying in the presence of sucrose also preserves the aqueous conformation and results in the formation of a glassy state. Comparison of shifts of the OH band with temperature indicates that sucrose/poly-L-lysine mixtures form a molecularly more densely packed glassy matrix, having a higher glass transition temperature (Tg), than sucrose alone. Whether direct interaction of sugar and polypeptide or glass formation is involved in the stabilization during slow air-drying was studied by drying in the presence of glucose or dextran. Compared with dextran (and sucrose to a lesser extent), glucose gives superior protection. Dried glucose has the lowest Tg and the best interacting properties. We conclude that either immobilization by fast air-drying or sufficient interaction with a protectant through hydrogen bonding (slow drying) plays the leading role in the preservation of the aqueous protein structure.