Salt Strength Research Articles

Numerical modelling of the role of salt in continental collision: An application to the southeast Zagros fold-and-thrust belt

The Zagros fold-and-thrust belt formed in the collision of Arabia with Central Iran. Its sedimentary sequence is characterised by the presence of several weak layers that may control the style of folding and thrusting. We use 2-D thermo-mechanical models to investigate the role of salt in the southeast Zagros fold-and-thrust belt. We constrain the crustal and lithospheric thickness, sedimentary stratification, convergence velocity, and thermal structure of the models from available geological and geophysical data. We find that the thick basal layer of Hormuz salt in models on the scale of the upper-mantle decouples the overlying sediments from the basement and localises deformation in the sediments by trench-verging shear bands. In the collision stage of the models, basement dips with +1° towards the trench. Including the basal Hormuz salt improves the fit of predicted topography to observed topography. We use the kinematic results and thermal structure of this large-scale model as the initial conditions of a series of upper-crustal-scale models. These models aim to investigate the effects of basal and intervening weak layers, salt strength, basal dip, and lateral salt distribution on deformation style of the simply folded Zagros. Our results show that in addition to the Hormuz salt at the base of the sedimentary cover, at least one intervening weak layer is required to initiate fold-dominated deformation in the southeast Zagros. We find that an upper-crustal-scale model, with a basal and three internal weak layers with viscosities between 5×1018 and 1019Pas, and a basement that dips +1° towards the trench, best reproduces present-day topography and the regular folding of the sedimentary layers of the simply folded Zagros.

An efficient system for in vitro propagation of Bouchea fluminensis (Vell.) Mold. (Verbenaceae)

This study aimed to establish and propagate in vitro plants of Bouchea fluminensis, a medicinal species known in Brazil as gervao-falso (false verbena), evaluating the influences of different growth regulators on in vitro multiplication and rooting stages, as well as examining ex vitro acclimatization of rooted plants. Explants were established on Murashige and Skoog medium at half strength of salts and vitamins without growth regulators. For multiplication, the explants were subjected to combinations of 6-benzyladenine (BA; 0, 2.5, 5.0 and 7.5 µM) and α-naphthalene-acetic acid (NAA; 0, 0.2, 0.4 and 0.6 µM). The medium found to induce the greatest number of shoot was that containing 5 µM of BA (NAA-free). For rooting, we evaluated three auxins (NAA, indole-3-acetic acid and indole-3-butyric acid; 0.1, 0.2, 0.3 and 0.4 µM), as well as a control. No differences were observed between the control and the other treatments. The auxin-free medium was deemed the most suitable, because it ensures the lowest cost in the micropropagation procedures. We obtained 100% survival of the acclimatized seedlings, and the plants showed normal vegetative and reproductive development, suggesting that the micropropagation did not alter the biological cycle of this species. The results show the importance and potential of micropropagation for biodiversity conservation of Bouchea fluminensis.

In vitro propagation of female Ephedra foliata Boiss. & Kotschy ex Boiss.: an endemic and threatened Gymnosperm of the Thar Desert.

Ephedra foliata Boiss. & Kotschy ex Boiss., (family - Ephedraceae), is an ecologically and economically important threatened Gymnosperm of the Indian Thar Desert. A method for micropropagation of E. foliata using nodal explant of mature female plant has been developed. Maximum bud-break (90%) of the explant was obtained on MS medium supplemented with 1.5mgl(-1) of benzyl adenine (BA) + additives. Explant produces 5.3 ± 0.40 shoots from single node with 3.25 ± 0.29cm length. The multiplication of shoots in culture was affected by salt composition of media, types and concentrations of plant growth regulators (PGR's) and their interactions, time of transfer of the cultures. Maximum number of shoots (26.3 ± 0.82 per culture vessel) were regenerated on MS medium modified by reducing the concentration of nitrates to half supplemented with 200mgl(-1) ammonium sulphate {(NH4) 2SO4} (MMS3) + BA (0.25mgl(-1)), Kinetin (Kin; 0.25mgl(-1)), Indole-3-acetic acid (IAA; 0.1mgl(-1)) and additives. The in vitro produced shoots rooted under ex vitro on soilrite moistened with one-fourth strength of MS macro salts in screw cap bottles by treating the shoot base (s) with 500mgl(-1) of Indole-3-butyric acid (IBA) for 5min. The micropropagated plants were hardened in the green house. The described protocol can be applicable for (i) large scale plant production (ii) establishment of plants in natural habitat and (iii) germplasm conservation of this endemic Gymnosperm of arid regions.

Controlling chitosan-based encapsulation for protein and vaccine delivery

Chitosan-based nano/microencapsulation is under increasing investigation for the delivery of drugs, biologics and vaccines. Despite widespread interest, the literature lacks a defined methodology to control chitosan particle size and drug/protein release kinetics. In this study, the effects of precipitation–coacervation formulation parameters on chitosan particle size, protein encapsulation efficiency and protein release were investigated. Chitosan particle sizes, which ranged from 300 nm to 3 μm, were influenced by chitosan concentration, chitosan molecular weight and addition rate of precipitant salt. The composition of precipitant salt played a significant role in particle formation with upper Hofmeister series salts containing strongly hydrated anions yielding particles with a low polydispersity index (PDI) while weaker anions resulted in aggregated particles with high PDIs. Sonication power had minimal effect on mean particle size, however, it significantly reduced polydispersity. Protein loading efficiencies in chitosan nano/microparticles, which ranged from 14.3% to 99.2%, were inversely related to the hydration strength of precipitant salts, protein molecular weight and directly related to the concentration and molecular weight of chitosan. Protein release rates increased with particle size and were generally inversely related to protein molecular weight. This study demonstrates that chitosan nano/microparticles with high protein loading efficiencies can be engineered with well-defined sizes and controllable release kinetics through manipulation of specific formulation parameters.

Nanoreticulations of etherified locust bean polysaccharide for controlled oral delivery of lamivudine

Herein, an aqueous solution of etherified locust bean polysaccharide (ELBP) containing lamivudine was reticulated in presence of trivalent aluminium (Al3+) ions to nanoscale level (43.82–197.70nm) by surfactant assisted homogenization-reticulation technique. The variation in aluminium chloride (AlCl3) strength (1.5–3.5% (w/v)) and drug:ELBP weight ratio (0.11–0.43) affected the properties of the nanoreticulations. Regardless of the variables, a maximum of ∼44% drug entrapment efficiency was noted. In simulated intestinal fluid (phosphate buffer solution, pH 7.4), the drug release rate was inversely proportional to the strength of AlCl3; but followed a proportional relationship with the drug:ELBP ratio. The mechanism of drug release shifted from Fickian diffusion to anomalous transport as the salt strength was increased above 2.5% (w/v). At intermediate drug:ELBP ratio, the drug release rate was regulated by polymer chain relaxation as opposed to simple diffusion mechanism. Fourier transform infrared spectroscopy did not show any evidence of chemical interaction between the drug and ELBP. Thermal analysis and X-ray diffraction studies suggested amorphous dispersion of drug in the nanoreticulations. Thus, the nanoreticulations were expected to absorb via intestine and phagocytosed by the virus-infected hepatic macrophages and hence could be useful for controlled delivery of lamivudine avoiding dose-dependent toxicity of the drug.

Optimization and quality assessment of adventitious roots culture in Panax quinquefolium L.

In this study, adventitious roots of Panax quinquefolium L. have been successfully established. The highest induction rate of roots was obtained in MS medium containing 3 mg L−1 IBA after 4 weeks of culture. The culture conditions of adventitious root were optimized and evaluated with response surface methodology. The best culture conditions for root growth seemed to be 0.75 salt strength MS medium, 4.70 g L−1 inoculum size and 40 days of culture. The active component contents of adventitious roots were compared with those of native roots. The total saponins content was found to be 16.28 mg g−1 in native root and 4.64 mg g−1 in adventitious root. The polysaccharide content of the adventitious root was 1.5 times higher than that in the native P. quinquefolium (30.54 vs. 20.28 mg g−1).

NaCl and KCl phase diagrams of kappa/iota-hybrid carrageenans extracted from Mastocarpus stellatus

The phase diagrams of kappa/iota-hybrid carrageenan (KI) in KCl and NaCl are reported for the first time, together with the large strain properties of obtained KI gels. KI shows salt specificity as phase diagrams in KCl and NaCl are different. These diagrams do not comply with those of a mixture of kappa- and iota-carrageenan (K + I). Concentrated KI solutions in NaCl up to 0.3 mol/L exhibit viscoelastic properties reminiscent from entangled neutral polymers with no aggregation. Both KI and K + I gels are strain hardening, and show a concentration scaling of the elasticity with exponents ranging from 1.2 to 3.2 depending on the type of salt and ionic strength. The strain at break of KI gels does not show salt specificity in contrast to K + I gels. In NaCl, KI gels are less brittle than K + I gels. In KCl, KI gels show the same level of strain at break as the corresponding carrageenan mixture.

Production of biomass and bioactive compounds by adventitious root suspension cultures of Morinda citrifolia (L.) in a liquid-phase airlift balloon-type bioreactor

To improve root growth and production of bioactive compounds such as anthraquinones (AQ), phenolics, and flavonoids by adventitious root cultures of Morinda citrifolia, the effects of aeration rate, inoculum density, and Murashige and Skoog (MS) medium salt strengths were investigated using a balloon-type bubble bioreactor. The possible mechanisms underlying changes in activities of enzymic (superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase) and nonenzymic (vitamin E) antioxidants, phenylalanine ammonia lyase, and stress levels (accumulation of hydrogen peroxide and proline, peroxidation of lipids) were also studied. Low aeration rate (0.05 vvm [air volume/culture volume/min]) accelerated accumulation of root fresh weight and dry weight (DW). High aeration rates (0.1 to 0.3 vvm) stimulated accumulation of AQ, phenolics, and flavonoids and reduced root growth. Low inoculum densities (5 and 10 g l–1) increased accumulation of those metabolites but inhibited root growth. Culture of adventitious roots with high concentrations of MS salts (1× and 1.5× MS) resulted in induction of oxidative stress that strongly inhibited root growth. Overall, an aeration rate of 0.05 vvm, 15 g l–1 inoculum density, and half-strength (0.5×) MS medium were optimal for enhancing accumulation of root dry biomass (4.38 g l–1), AQ (103.08 mg g–1 DW), phenolics (54.81 mg g–1 DW), and flavonoids (49.27 mg g–1 DW).

In vitro flowering and seed production in regenerated shoots of Cleome viscosa

A protocol was developed for induction of in vitro flowering and seed production on shoots regenerated from nodal explants of Cleome viscosa. The multiple shoots differentiated through bud breaking on Murashige and Skoog's (MS) medium with 2.0mgL−1 benzylaminopurine (BAP). These regenerated shoots were further amplified on MS medium with 0.5mgL−1 BAP. Vegetative to reproductive phase transition occurred in the cultures affected by plant growth regulators (PGRs), sucrose concentrations, strength of MS salts and light. Flower buds initiated from the regenerated shoots on half strength of MS salts with 0.25mgL−1 of BAP+0.5mgL−1of IBA (indole-3 butyric acid) and 40gL−1 sucrose. These flower buds opened under low light (10–15μmolm−2s−1) condition with 15h/9h photoperiod within 3 weeks of culture initiation. The shoots did not flower in the dark. Though smaller in size, the in vitro generated flowers were morphologically comparable to the natural flowers. Fruits were set in the cultures within 5 weeks. The seeds produced in culture through self-pollination were collected from mature fruits and tested viable. Our study demonstrates that the life cycle of C. viscosa can be completely controlled under in vitro conditions without any seasonal effect. The process can be useful for (i) large scale production of plants, (ii) understanding the process of flowering, (iii) controlled breeding, and (iv) production of seeds under in vitro conditions.

Micropropagation of Elite Genotypes of Castanea Sativa (MILL.)

Sprouted buds of eight mature plus-trees of Castanea sativa were collected from two natural populations (Mt. Paiko and Mt. Hortiatis, Greece). Explants were cultured on Murashige and Skoog (MS) medium (three concentrations of macro and micro-elements) combined with three concentrations of BAP (6-Benzylaminopurine). Results were evaluated based on three multiplication traits: (a) number of shoots produced, (b) length of the longest shoot segments and (c) percentage of responsive explants. A high genotype-dependant variation for the number of shoots produced per explant was detected. MS medium at full salt strength and 0.2 mg l-1 BAP provided the best results based on the multiplication traits measured. Elite mature tree P-2 proved to be highly favourable for multiplication. Rooting was attempted on ½ MS medium at five different NAA concentrations. Successful rooting (56%) was obtained by using 0.50 mg l-1 NAA in vermiculite medium after eight weeks. These results indicate that the P-2 genotype can be micropropagated from the protocol developed for ornamental purposes, clonal testing and tree improvement applications.Â

Effects of Background Fluid on the Efficiency of Inactivating Yeast with Non-Thermal Atmospheric Pressure Plasma

Non-thermal plasma at atmospheric pressure has been actively applied to sterilization. However, its efficiency for inactivating microorganisms often varies depending on microbial species and environments surrounding the microorganisms. We investigated the influence of environmental factors (surrounding media) on the efficiency of microbial inactivation by plasma using an eukaryotic model microbe, Saccharomyces cerevisiae, to elucidate the mechanisms for differential efficiency of sterilization by plasma. Yeast cells treated with plasma in water showed the most severe damage in viability and cell morphology as well as damage to membrane lipids, and genomic DNA. Cells in saline were less damaged compared to those in water, and those in YPD (Yeast extract, Peptone, Dextrose) were least impaired. HOG1 mitogen activated protein kinase was activated in cells exposed to plasma in water and saline. Inactivation of yeast cells in water and saline was due to the acidification of the solutions by plasma, but higher survival of yeast cells treated in saline may have resulted from the additional effect related to salt strength. Levels of hydroxyl radical (OH.) produced by plasma were the highest in water and the lowest in YPD. This may have resulted in differential inactivation of yeast cells in water, saline, and YPD by plasma. Taken together, our data suggest that the surrounding media (environment) can crucially affect the outcomes of yeast cell plasma treatment because plasma modulates vital properties of media, and the toxic nature of plasma can also be altered by the surrounding media.

In vitro propagation and micromorphological studies of Cleome gynandra: a C4 model plant closely related to Arabidopsis thaliana

We developed a micropropagation protocol for Cleome gynandra, a C4 model plant with medicinal importance. Surface-sterilized nodal segments obtained from 1 to 2-month-old field grown plant were used as explants for culture establishment and plant regeneration. Multiple shoots differentiated through bud breaking on Murashige and Skoog (MS) medium with different concentrations of benzyladenine (BA) and kinetin (Kin). The optimum shoot differentiation occurred on medium with 1.5 mg l−1 BA. Out of various concentrations and combinations of cytokinins and auxins, MS medium containing 0.5 mg l−1 BA and 0.1 mg l−1 IAA (indole-3-acetic acid) was found best for shoot multiplication. However, the differentiated shoots exhibited hyperhydration, leaf curling and early leaf fall during subculturing. To overcome these problems, regenerated shoots were transferred to the modified MS medium with reduced nitrates (825 mg l−1 NH4NO3 and 950 mg l−1 KNO3) and 100 mg l−1 (NH4)2SO4. The micropropagated shoots were rooted (i) in vitro on one-fourth strength of MS salts with 0.25 mg l−1 each of IBA (indole-3 butyric acid) and NOA (2-naphthoxyacetic acid) + 100 mg l−1 activated charcoal, and (ii) ex vitro, by treating the shoot base(s) with 200 mg l−1 of IBA for 3 min and transferred to soilrite moistened with one-fourth strength of MS macro salts in culture bottles. The plants were hardened in the greenhouse with 85 % survival rate. Micromorphological studies of the plants were conducted during hardening with reference to development and changes in vein spacing, glandular trichome and stomata. In comparison to leaves under in vitro condition, higher density of veins and glandular trichomes was observed in the leaves of hardened plants. In addition, stomata became functional during hardening which were non-functional under in vitro condition.

Induced-charge electro-osmosis of polymer-containing fluid around a metallic rod

Induced-charge electro-osmotic (ICEO) flow of polymer-containing electrolyte solution around a cylindrical gold-coated stainless steel rod under AC electric field is measured by micro-particle image velocimetry (micro-PIV) for the first time. The ICEO flows as functions of the amount of non-ionic PEG (polyethylene glycol), cationic PDADMA (polydiallyldimethylammonium chloride), and anionic PVSASS (polyvinylsulfonic acid sodium salt) polymers added into the salt solution, frequency, and strength of the AC electric field are measured. The ICEO flow of polymer-containing fluid around the rod is quadrupolar with four vortices and is proportional to the square of imposed electric field. The ICEO flow velocity exponentially decreases with an increased concentration of neutral PEG. Ionic polyelectrolytes significantly increase ICEO velocities due to the enriched net charge within the induced electric double layer arising from the electrostatic interaction between the polarized rod’s surface and the charged polyelectrolytes in ionic polymer solution. In addition, polymer concentration affects the dependence of the ICEO flow on the frequency of AC electric field.

True-triaxial compressive strength of Maha Sarakham salt

True triaxial compressive strengths of the Maha Sarakham salt are experimentally determined by using a polyaxial load frame. The salt specimens with nominal dimensions of 5.4×5.4×10.8cm3 are loaded to failure with the minimum principal stress, σ3, varying from 0 to 7MPa, and the intermediate principal stress, σ2, varying from 0 to 80MPa. The major principal (axial) stress is increased at a rate of 0.5–1.0MPa/s until failure occurs. Based on the Coulomb criterion the internal friction angle determined from the triaxial loading condition (σ2=σ3) is 50°, and the cohesion is 5.0MPa. The elastic parameters of the salt tend to be independent of σ2 for the applied stress range. The effect of σ2 on the salt strength can be described best by the modified Wiebols and Cook criterion with a mean misfit of 3.5MPa. The (power law) Mogi criterion underestimates the salt strength, particularly under high σ3 values. The modified Lade and 3-D Hoek & Brown criteria overestimate the strength at all levels of σ3. The Coulomb and Hoek & Brown criteria cannot describe the salt strengths beyond the condition where σ2=σ3, as they cannot incorporate the effects of σ2. Both circumscribed and inscribed Drucker–Prager criteria severely underestimate σ1 at failure for all stress conditions, showing the largest mean misfit of 19.5MPa.

Influence of medium salt strength and nitrogen source on biomass and metabolite accumulation in adventitious root cultures of Pseudostellaria heterophylla

We investigated the effects of medium salt strength and ammonia/nitrate ratio on biomass production and metabolites accumulation of adventitious root. The medium with full-strength Murashige and Skoog (MS) reached the highest growth rate (16.77), and the contents of saponin and polysaccharide reached the peak (i.e., 0.65 and 24.85 %) at 3/4 MS and 1 MS, respectively. In case of ammonia/nitrate ratio, a NH4 +/NO3 − ratio of 20:40 was optimal for the production of biomass and polysaccharide (23.27 %). In contrast, the content of saponin achieved the optimum (0.74 %) at a NH4 +/NO3 − ratio of 30:30. In 5-L balloon-type bubble bioreactor (BTBB) cultures, an approximately 23-fold increase in biomass was recorded. The fresh weight (FW) and dry weight (DW) were 72.78 and 6.79 g per bioreactor with the contents of saponin (0.62 %) and polysaccharide (17.32 %), respectively. It indicated potential application to produce adventitious roots of pseudostellaria heterophylla with bioreactors on large scale in commercial.

In vitro propagation of Gerbera (Gerbera jamesonii Bolus)

Gerbera plant Gerbera jamesonii is classified according to the flower colors to four strains: white, yellow, pink and purple. Capitulum and scape explants were tested on MS medium in half or full salts strength, supplemented with different combinations of plant growth regulators cytokinins kintin (Kin) and benzel adinine (BA), auxin indolacitic acid (IAA). Results revealed that the capitulum showed better response to shoot formation 64.13% whereas the scape did not show response. Yellow flowers showed higher response in shoot formation 37.5% than other strains. growth regulators combination BA and IAA (3.0 + 0.1) mg/L respectively showed better response for shoot multiplication. Auxin IBA (0.5) mg/ L gave better rooting percentage 60% than other auxins IAA and NAA all concentrations. The acclimatization of the gerbera was 78.59%.

Influencing factors on culture of medicinal plants adventitious roots

With the modernization of traditional Chinese medicine, medicinal plants resources cannot meet the request of Chinese medicine industry. Medicinal plants adventitious roots culture in a large scale is an important way to achieve Chinese medicine industrialization. However, how to establish good adventitious roots culture system is its key, such as plant hormones, explant, sucrose, innoculum and salt strength.

Scale-up of adventitious root cultures of Echinacea angustifolia in a pilot-scale bioreactor for the production of biomass and caffeic acid derivatives

In an attempt to scale-up of adventitious root cultures of Echinacea angustifolia for the production of biomass and caffeic acid derivatives, i.e. echinacoside, chlorogenic acid, cichoric acid, caftaric acid, and cynarin, the effects of Murashige and Skoog (MS) medium dilutions, and initial sucrose concentrations were investigated in a 5-L airlift bioreactor. In addition, the kinetics of adventitious root growth and accumulation of secondary metabolites were also studied. The greatest root dry weight (6.50 g L−l) and accumulation of total phenolics [22.06 mg g−1 DW (dry weight)], total flavonoids (5.77 mg g−1 DW) and total caffeic acid derivatives (10.63 mg g−1 DW) were obtained at quarter-strength MS medium. Of the various gradients of sucrose tested, 5 % sucrose supplementation was regarded as an optimal concentration for enhancing productivity of biomass and bioactive compounds. Neither higher salt strength (3/4–2 MS) nor sucrose concentrations (7 and 9 %) showed promotive effect on root growth and metabolite production. The kinetic studies revealed that 4 weeks of culture period is the optimal time to achieve highest productivity of metabolites. Based on these results, a large-scale (20 L) and a pilot-scale (500 L) adventitious root culture system was established. In the pilot-scale bioreactor, adventitious roots were elicitor-treated with 100 μM methyl jasmonate (MJ) on day 28. After 1 week of elicitation, 1.75 kg dry root biomass was harvested containing 60.41 mg g−1 DW of total phenolics, 16.45 mg g−1 DW of total flavonoids, and 33.44 mg g−1 DW of total caffeic acid derivatives. Among the caffeic acid derivatives, the accumulation of echinacoside (the major bioactive compound) in MJ-treated adventitious roots grown in the 500-L bioreactor was the highest (12.3 mg g−1 DW), which is approximately threefold more than the non-MJ-treated roots cultured in 5- and 20-L bioreactors.

Propagação e conservação in vitro de vetiver

O vetiver (Chrysopogon zizanioides) é um capim perene com características físico-químicas e agronômicas importantes que o torna uma espécie destaque. De suas raízes é extraído um óleo essencial utilizado amplamente na produção de perfumes e devido à sua baixa volatilidade, como fixador de odor. Esse trabalho teve como objetivo desenvolver um protocolo de propagação e de conservação in vitro de vetiver. Para o ensaio de multiplicação in vitro testaram-se combinações dos reguladores de crescimento BAP e ANA. Na aclimatização foram testados substratos contendo pó de coco e/ou vermiculita suplementado com calcário, fertilizante NPK (3-12-6) e concentrações dos sais do meio MS. Nos ensaios de conservação in vitro foram avaliadas as temperaturas de 18 e 25°C, reguladores osmóticos (sacarose, manitol e sorbitol), o inibidor de crescimento ABA e diferentes concentrações dos sais MS. Verificou-se que a micropropagação de vetiver UFS-VET003 é promovida em meio MS líquido acrescido de 3,33 mg L-1 de BAP, sendo a etapa de enraizamento das brotações proporcionada em meio MS básico, também líquido. Para aclimatização recomenda-se o substrato PBC. A conservação in vitro é possível em meio MS semissólido com 25% dos sais MS e temperatura de 18°C por um período de 270 dias.

The role of salt concentration and magnesium binding in HIV-1 subtype-A and subtype-B kissing loop monomer structures

The subtype-B monomers of the human immunodeficiency virus type-1 (HIV-1) have experimentally been shown to dimerize at high salt concentration or in the presence of magnesium, while the dimerization of the subtype-A monomers requires magnesium binding at the G273 or G274 phosphate groups regardless of salt concentration. We used explicit solvent molecular dynamics (MD) simulations to investigate the conformational changes in subtype-A and -B monomers in different salt concentrations, and we found that our MD simulation results are consistent with those of experiments. At low salt concentration, hairpin loop structures of both subtypes were deformed and bases in the hairpin loop were turned inside. At high salt concentrations, the subtype-B monomer maintained the hairpin loop shape and most bases in the hairpin loop pointed out, while the subtype-A monomer showed a severe deformation. We also found that the flanking bases in the subtype-B stabilize the hairpin loop, while the flanking base G273 in the subtype-A caused a significant deformation. However, a bound magnesium ion at the G273 or G274 phosphate groups controlled the behavior of the G273 base and prevented the subtype-A monomer from deformation. We also applied restraints to both subtypes to examine the role of high salt concentration or magnesium binding. While restraints were applied, both subtypes at 0 M salt concentration maintained their shapes. However, when restraints were removed, they deformed significantly. Therefore, we suggest that the dimerization of both subtypes requires the proper conformation of the monomers which is induced by the appropriate salt strength and magnesium ion binding.