Salt Concentration In Medium Research Articles

Folding dynamics and conformational heterogeneity of human telomeric G-quadruplex structures in Na+ solutions by single molecule FRET microscopy.

G-quadruplex structures can occur throughout the genome, including at telomeres. They are involved in cellular regulation and are potential drug targets. Human telomeric G-quadruplex structures can fold into a number of different conformations and show large conformational diversity. To elucidate the different G-quadruplex conformations and their dynamics, we investigated telomeric G-quadruplex folding using single molecule FRET microscopy in conditions where it was previously believed to yield low structural heterogeneity. We observed four FRET states in Na+ buffers: an unfolded state and three G-quadruplex related states that can interconvert between each other. Several of these states were almost equally populated at low to medium salt concentrations. These observations appear surprising as previous studies reported primarily one G-quadruplex conformation in Na+ buffers. Our results permit, through the analysis of the dynamics of the different observed states, the identification of a more stable G-quadruplex conformation and two transient G-quadruplex states. Importantly these results offer a unique view into G-quadruplex topological heterogeneity and conformational dynamics.

Novel superabsorbent copolymers of partially neutralized methacrylic acid and acrylonitrile: synthesis, characterization and swelling characteristics

Novel superabsorbent copolymers (SAP) based on random copolymers of sodium methacrylate, methacrylic acid, and acrylonitrile (ACN) of varying compositions and cross-link densities were synthesized by free radical polymerization and were characterized. ACN content in the copolymers varied from 0 to 15 mol%. The SAPs were capable of absorbing 350–990 times their weight of water and 60–130 times their weight of saline (0.3 wt. % solution of sodium chloride in deionized water) depending on the composition and cross-link density of the copolymer. Swelling of the copolymers followed first-order kinetics with non-Fickian swelling behavior in deionized water. Water absorbency (Sw) was found to decrease with pressure on the gel side and a pressure coefficient (dSw/dp) of −0.6%/Pa was estimated for a given composition of the copolymer. Strength of the hydrogels increased with increasing cross-link density. Shear modulus of the hydrogels was found to vary from 1000 to 6000 Pa depending on the composition and cross-link density. Higher cross-link density of the SAP and higher salt concentration of the swelling medium reduced the swelling ratio, while higher extent of neutralization and lower salt concentration of the medium enhanced it. Different copolymer hydrogels were able to retain 50–78% of absorbed water at 37 °C after a period of 20 h, with the systems having lower ACN content retaining higher amount of water. The copolymers exhibited absorbency in the range of 1500–2000% by weight under a pressure of 6200 Pa when swollen in 0.9% aqueous solution of sodium chloride. Increase in ionic strength of the medium, pressure on the hydrogel, and temperature (of the medium) were proven to decrease the swelling commensurate with the thermodynamics of the system.

Parallelized small-scale production of uniformly 13C-labeled cell extract for quantitative metabolome analysis

The need for quantitative intracellular metabolome information is central to modern applied biotechnology and systems biology. In most cases, sample preparation and metabolite analysis result in degradation of metabolites and signal suppression due to metabolite instability and matrix effects during LC–MS analysis. Therefore the application of uniformly (U) 13C-labeled cell extract as an internal standard has gained interest in recent years. In this study a multiple-step protocol has been developed for efficient preparation of U-13C-labeled Escherichia coli cell extracts in stirred-tank bioreactors on a milliliter scale with a minimal supply of costly 13C-labeled substrate. Significant reduction of fermentation medium salt concentration in the U-13C-labeled cell extract was achieved to reduce ion-suppression effects during mass-spectrometric analysis. Additionally, variation of reaction conditions in parallel-operated stirred-tank bioreactors on a milliliter scale enables the simultaneous preparation of U-13C-labeled cell extracts with varying metabolite concentrations, which is shown by an example of the labeled phosphoenolpyruvate level in E. coli.

Оценка порога вкусовой чувствительности к поваренной соли как одного из факторов риска артериальной гипертензии у школьников Тюмени

Aim. To study the prevalence of the taste sensitivity threshold for salt (TSTS) as one of the main risk factor for hypertension in Tyumen city schoolchildren. Material and methods. The single-period epidemiologic study conducted in the population of 7-17 y. o. schoolchildren from one of the districts of Tyumen (2004-2006), chosen by a random assignment method, with a quantity of 2640 persons (1308 boys, 1332 girls), with response rate 87,7%. In schoolchildren of 9-17 y. o. (880 boys, 936 girls), the TSTS measured using modified Henkin R et al. method (described by Konstantinov E. N. et al., 1983). Results. The prevalence of high level of TSTS in a population of schoolchildren was 14,8%, average TSTS had 75,8% of schoolchildren, in 9,5% of persons low TSTS was identified. Persons with high TSTS were met almost in 2 times often among boys compared with girls, and in 1,5 times among adolescents with simultaneously elevated systolic and diastolic blood pressure (BP), than among schoolchildren with normal BP levels (p<0,05).Adolescents 14-17 years of age with elevated diastolic blood pressure were observed higher tangible medium salt concentration. The relation between TSTS and the degree of increase in blood pressure in adolescent’s, from medium to strong, was revealed by paired correlation analysis. Conclusion. The results showed high prevalence of the high TSTS in Tyumen schoolchildren population, relation between TSTS and the severity of BP increase in youths.

Micropropagation of PLUCHEA LANCEOLATA (Oliver &amp; Hiern.) Using Nodal Explant

Abstract Pluchea lanceolata is an important medicinal plant of Asteraceae family known for its anti-arthritic and anti-inflammatory activity. A protocol was established for micropropagation of P. lanceolata using nodal explants. Nodal explants were inoculated onto Murashige and Skoog (1962) - MS medium supple–mented with 6-benzylaminopurine (BAP), kinetin (Kin), thidiazuron (TDZ) and 2iP (2-isopentenyladenine) at various concentrations (0.0, 0.5, 1.0, 1.5 and 2.0 mg·dm-3). The highest multiplication rate was obtained for nodal explants cultured on MS medium, supplemented with 0.5 mg·dm-3 thidiazuron (TDZ). In vitro raised shoots were successfully rooted on ½ mineral salt concentration of MS medium supplemented with 1.0 mg dm-3 IBA.

Production of poly-3-(hydroxybutyrate-co-hydroxyvalerate) by Haloferax mediterranei using rice-based ethanol stillage with simultaneous recovery and re-use of medium salts

Haloferax mediterranei holds promise for competitive industrial-scale production of polyhydroxyalkanoate (PHA) because cheap carbon sources can be used thus lowering production costs. Although high salt concentration in production medium permits a non-sterile, low-cost process, salt disposal after process completion is a problem as current environmental standards do not allow total dissolved solids (TDS) above 2000 mg/l in discharge water. As the first objective of this work, the waste product of rice-based ethanol industry, stillage, was used for the production of PHA by H. mediterranei in shake flasks. Utilization of raw stillage led to 71 ± 2% (of dry cell weight) PHA accumulation and 16.42 ± 0.02 g/l PHA production. The product yield coefficient was 0.35 while 0.17 g/l h volumetric productivity was attained. Simultaneous reduction of BOD5 and COD values of stillage by 83% was accomplished. The PHA was isolated by osmotic lysis of cells, purification by sodium dodecyl sulfate and organic solvents. The biopolymer was identified as poly-3-(hydroxybutyrate-co-15.4 mol%-hydroxyvalerate) (PHBV). This first report on utilization of rice-based ethanol stillage for PHBV production by H. mediterranei is currently the most cost effective. As the second objective, directional properties of decanoic acid together with temperature dependence of water solubility in decanoic acid were applied for two-stage desalination of the spent stillage medium. We report for the first time, recovery and re-use of 96% of the medium salts for PHA production thus removing the major bottleneck in the potential application of H. mediterranei for industrial production of PHBV. Final discharge water had TDS content of 670 mg/l.

The influence of ferric (III) citrate on ATP-hydrolases of Desulfuromonas acetoxidans ІМV В-7384

Desulfuromonas acetoxidans obtains energy for growth by the anaerobic oxidation of organic compounds with the carbon dioxide formation. It was found that ferrum and manganese are used as terminal electron acceptors in the processes of anaerobic respiration, such as dissimilative Fe3+- and Mn4+-reduction, carried out by these bacteria (Lovely, 1991). D. acetoxidans ІМV B-7384 can be used as anode biocatalyst in microbial fuel cell with high electron recovery through acetate oxidation to the electric current as a result of electron transfer to the anode or 3d-type transition metals, such as ferrum and manganese, in the process of their reduction. Investigation of biochemical changes of D. acetoxidans ІМV B-7384 under the influence of Fe (III) compounds is important for optimization of the process of bacterial electricity generation. ATP-hydrolase is located in cytoplasmic membrane, and its subunits are exposed to both the cytoplasm and the external environment. Therefore, the changes of that enzyme activity can be used as an indicator of various stress exposure. Presence of ferric iron ions in the bacterial growth medium could catalyze generation of organic reactive oxygen species, such as peroxyl (ROO-) and alkoxyl (RO-) radicals. Lipid peroxidation is one of the main reasons of cell damage and it’s following death under the influence of reactive oxygen metabolites. It is known that lipid peroxidation and membrane transport processes are somehow interrelated, but mechanisms of such interaction are still unidentified. In our previous researche we have shown the influence of ferric (III) citrate on the intensity of lipid peroxidation of D. аcetoxidans ІМV В-7384. Significant increase of the content of lipid peroxidation products (lipid hydroperoxides, conjugated dienes and malondialdehyde) in bacterial cells has been observed under the addition of ferric (III) citrate into the cultural medium. The increase of the concentration of lipid peroxidation products in bacterial cells confirms free radical mechanism of oxidation of polyunsaturated fatty acids. Thus, for fulfiling complete analyses of cell response against oxidative stress it was reasonable to investigate the influence of ferric (III) citrate on specific ATP-hydrolase activity, Na+, K+-ATP-hydrolase activity and Mg2+-ATP-hydrolase activity of D. acetoxidans ІМV В-7384. Bacteria were cultivated in the modified Postgaite C medium during four days under the anaerobic conditions and temperature +27°С with addition from 10 to 20 mM of ferric (III) citrate into the growth medium. Control samples didn’t contain investigated metal salt. Chosen concentrations of metal salt caused inhibition of bacterial growth by 20–50%. Activities of ATP-hydrolases were investigated as described. It was shown, that specific ATP-hydrolase activity of D. acetoxidans ІМV В-7384 is changing in dependance on duration of ferric (III) citrate exposure and concentration of the metal salt. Addition of the ferric (III) citrate in relatively low concentrations (10–12 mM) causes increasing of specific ATP-hydrolase activity of D. acetoxidans IMV B-7384 in comparison with control. Activity of investigated enzymes was inhibited under the increasing of metal salt concentration in bacterial growth medium. Increase of duration of D. acetoxidans IMV B-7384 cultivation causes decrease of ATP-hydrolase activity. Addition of ferric (III) citrate causes simultaneous increasing of Na+, K+-ATP-hydrolase activity and inhibition of Mg2+-ATP-hydrolase activity during four days of bacterial cultivation.

Preparation and Controlled Drug Release Characteristics of Thermoresponsive PEG/Poly (NIPAM-co-AMPS) Hydrogels

Thermosensitive hydrogels were prepared by free radical polymerization of N-isopropylacrylamide (NIPAM) and 2-acrylamido-2-methylpropanesulphonic acid (AMPS) in presence of polyethylene glycol (PEG) as macroinitiator. The incorporation of functional monomer in the hydrogel was confirmed by infrared spectroscopy. The equilibrium swelling ratio (ESR), deswelling rate, volume transition temperature, and surface morphology of synthesized hydrogels are found to be dependent on concentration of AMPS monomer in the feed composition. The equilibrium swelling ratio (ESR) and water retention properties increase with increasing AMPS concentration in hydrogels and decrease with increasing salt concentration in external medium. The hydrogel with high dose of AMPS has high loading efficiency of theophylline drug, whereas the in-vitro release of the drug is delayed for a prolonged period in swollen gels above LCST of PNIPAM.

Tipo de explante e diferentes concentrações de sais em meio de cultura MS no estabelecimento in vitro de Aniba canelilla

The peel - precious ( Aniba canelilla ) is a plant species native to the Amazon region , with economic potential in silvicultural terms , the production of perfumes and cosmetics . However , one limitation to the domestication of the species is the absence of propagation methods . The objective of this study was to evaluate the effect of explant type and different salt concentrations of MS medium in their establishment in vitro . Shoot tips ( 1.5 cm ) and nodal segments were used with two gems, isolated from bark - precious seedlings maintained in the greenhouse . The treatments consisted of two types of explants and six concentrations of salts in MS medium plus 15 or 30 g L- 1 sucrose and disinfectants . It was found that the nodal segment is less sensitive to treatments performed disinfestation and decontamination showed higher successful in survival and in vitro establishment of shell - precious.

Peptide-Surface Adsorption Free Energy Comparing Solution Conditions Ranging from Low to Medium Salt Concentrations

Multi-technique methods involving surface plasmon resonance spectroscopy and atomic force microscopy provide experimental data for the characterization of peptide adsorption on self-assembled monolayers. A comparative study is carried out in phosphate-buffered saline (PBS) and potassium phosphate-buffered (PPB) water to determine the influence of the salt concentration on the adsorption behavior (see figure; ΔG(0)(ads) : free energy of peptide adsorption, F(des) : force required for peptide desorption).

Higher salt preference in heart failure patients

Heart failure (HF) is a complex syndrome that involves changes in behavioral, neural and endocrine regulatory systems. Dietary salt restriction along with pharmacotherapy is considered an essential component in the effective management of symptomatic HF patients. However, it is well recognized that HF patients typically have great difficulty in restricting sodium intake. We hypothesized that under HF altered activity in systems that normally function to regulate body fluid and cardiovascular homeostasis could produce an increased preference for the taste of salt. Therefore, this study was conducted to evaluate the perceived palatability (defined as salt preference) of food with different concentrations of added salt in compensated chronically medicated HF patients and comparable control subjects. Healthy volunteers ( n = 25) and medicated, clinically stable HF patients ( n = 38, NYHA functional class II or III) were interviewed and given an evaluation to assess their preferences for different amounts of saltiness. Three salt concentrations (0.58, 0.82, and 1.16 g/100 g) of bean soup were presented to the subjects. Salt preference for each concentration was quantified using an adjective scale (unpleasant, fair or delicious). Healthy volunteers preferred the soup with medium salt concentration ( p = 0.042), HF patients disliked the low concentration ( p < 0.001) and preferred the high concentration of salted bean soup ( p < 0.001). When compared to healthy volunteers, HF patients demonstrated a significantly greater preference for the soup with a high salt concentration ( p = 0.038). It is concluded that medicated, compensated patients under chronic treatment for HF have an increased preference for salt.

Bacillus amyloliquefaciens DL-3의 carboxymethylcellulase를 재조합 균주 E. coli JM109/DL-3에서 생산하는 배지의 염 농도를 최적화하기 위한 통계학적 실험 방법의 비교

The optimal concentrations of salts in medium for cell growth and the production of carboxymethylcellulase (CMCase) by a recombinant E. coli JM109/DL-3 were established using two statistical methods: orthogonal array method (OAM) and response surface method (RSM). The analysis of variance (ANOVA) of data based on OAM indicated that K 2 HPO 4 gave maximum sum of square (S) and percentage contribution (P) for cell growth as well as production of CMCase. The optimal concentrations of K 2 HPO 4 , NaCl, MgSO 4 ?7H 2 O, and (NH 4 ) 2 SO 4 in medium for cell growth extracted by Qualitek-4 (W32b) Software were 10.0, 1.0, 0.2, and 0.6 g/l, respectively, whereas those for the production of CMCase by E. coli JM109/DL-3 were 5.0, 1.0, 0.4, and 0.6 g/l. The analysis of variance (ANOVA) resulting from RSM indicated that a highly significant salt for cell growth was K 2 HPO 4 (probe>F less than 0.0001), whereas K 2 HPO 4 and MgSO 4 ?7H 2 O were significant for the production of CMCase. The optimal concentrations of K 2 HPO 4 , NaCl, MgSO 4 ?7H 2 O, and (NH 4 ) 2 SO 4 for cell growth extracted by Design Expert Software were 7.44, 1.08, 0.22, and 0.88 g/l, respectively, whereas those for production of CMCase were 5.84, 0.69, 0.28, and 0.54 g/l. The optimal concentrations of salts and their influences on cell growth and production of CMCase extracted by OAM were almost the same as those by RSM. Production of CMCase by a recombinant E. coli JM109/DL-3 under optimized concentration of salts was 1.93 times higher than that by Bacillus amyloliquifaciens DL-3.

Fermentation optimization to improve production of antagonistic metabolites by Bacillus subtilis strain BS501a

To improve antagonistic metabolites production of Bacillus subtilis strain BS501a, physical parameters of fermentation and metal inorganic salts in medium, namely initial pH value, culture temperature, fermentation time, concentrations of CaCl2, FeSO4, ZnSO4, MnSO4 and MgSO4, were optimized using one-factor-at-a-time and orthogonal tests. The results show that the optimal physical parameters of fermentation are an initial pH of 7.0, a culture temperature of 30 °C, and a fermentation time of 48 h. The optimal concentrations of metal inorganic salts in basal medium are 10.2 mmol/L CaCl2, 0.4 mmol/L FeSO4, 3.5 mmol/L ZnSO4, 0.6 mmol/L MnSO4 and 2.0 mmol/L MgSO4. Among the metal inorganic salts, MgSO4 and MnSO4 play important roles in the improvement of the antagonistic metabolites production of B. subtilis strain BS501a; especially, MgSO4 contributes a highly significant effect. The average diameter of inhibition zone of the BS501a filtered fermentation supernatant (FFS) cultured in the optimal fermentation conditions against Magnaporthe grisea DWBJ329 reaches 71.4 mm, and there is 2.4-fold increase in antifungal activity as compared with 21.2 mm under the pre-optimized conditions.

Preparation and investigation of a cross-linked hyaluronan nanoparticles system

The present paper describes the preparation and characterization of hydrophilic hyaluronan nanoparticles formed by cross-linking of hyaluronic acid (HA) with 2,2′(ethylenedioxy)bis(ethylamine) in the presence of water-soluble carbodiimide (CDI) in aqueous media. The particle size of cross-linked nanosystems was measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), transmittance by UV–VIS spectrophotometry, gel permeation chromatography (GPC) and rheology to characterize the physico-chemical properties. The aqueous nanosystems prepared were stable, transparent or mildly opalescent with values of transmittance above 91%. It was observed, that a fraction of particles with size less than 20 nm, has been released during the purification by diafiltration. It was established that the hydrodynamic size of cross-linked HA nanoparticles can be controlled by variation of the reaction conditions such as concentration of HA, salt concentration of media, ratio of cross-linker and the final pH of the reaction mixture.

Micropropagation of Embelia ribes Burm f. through proliferation of adult plant axillary shoots

Micropropagation of Embelia ribes was achieved through proliferation of axillary shoots obtained from mature plants. Nodal shoot segments, collected March–May, exhibited high-frequency (75%) shoot initiation when cultured on Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ) at 1.13 µM and indole-3-butyric acid (IBA) at 0.49 µM. Subculture of sprouted shoots from the original explants on medium containing TDZ (1.13 and 0.45 µM) during the first and second subcultures was found essential for further shoot proliferation, while inhibition of shoot elongation by TDZ could be overcome by transferring shoot cultures onto MS medium containing 6-benzylaminopurine (BAP; 11.10 µM) for the third subculture. Treating the explants with an antioxidant mixture of 568 µM ascorbic acid, 119 µM citric acid, and 307 µM glutathione prior to inoculation, coupled with subculture at 2-wk intervals onto fresh medium, both helped to reduce browning of the explants and facilitated production of five to six shoots/explant. MS medium supplemented with BAP (4.44 µM) and IBA (0.49 µM) induced shoot multiplication, producing five to six shoots/explant with a shoot length of 3 to 4 cm over a 4-wk culture period. Shoots of 3 to 4 cm in length exhibited 100% rooting within 4 wk after transfer to media containing half the nutrient salt concentration of MS medium with 3.69 µM IBA. Ex vitro rooting in the greenhouse from the in vitro shoots treated with 4.93 µM IBA for 30 min exhibited 95% rooting in soilrite™ medium in a 4-wk period. About 85% of micropropagated plants were established successfully in root trainers. Three-month-old, hardened plants could further be successfully established in the field. In 1 yr, by using the above protocol, 3,200 plants could be produced from a single shoot and 2,700 could be established in the field.

Characterization Of Phosphoinositide Monolayers By Infrared Spectroscopy And Epifluorescence Microscopy At The Air/water Interface

Phosphoinositides have been shown to mediate a large variety of important physiological processes by affecting the activity and the localization of membrane associated proteins. Phosphoinositide properties are largely determined by the characteristics of their headgroup, which at physiological pH is highly charged but is also capable of hydrogen bond formation. For phosphoinositide mediated signaling events to occur, it requires the local enrichment of phosphoinositides, which depend on the interchange between attractive and repulsive forces. Factors expected to affect mutual phosphoinositide interaction are pH, cations, or positively charged proteins. We have characterized the structural properties of dipalmitoyl phosphatidylinositol mono-, bis- and trisphosphate monolayer films at the air/water interface by infrared reflection-absorption spectroscopy (IRRAS) as well as by direct visualization of domain formation of each phosphoinositide derivative by epifluorescence microscopy in the presence of low and high monovalent salt concentrations. It has been observed that on pure water subphases the surface pressure/area (Π/A) isotherms for all phosphoinositide derivatives were characteristic for a condensed monolayer whereas a monolayer expansion was found for medium (10 mM) and high salt concentrations (150 mM). IRRAS measurements showed that this was associated with a larger molecular tilt angle and a reduced acyl chain order. Using epifluorescence microscopy, domain formation has been observed for each phosphoinositide derivative as the monolayer goes from a liquid phase to the liquid condensed phase. In addition, membrane organization can be affected by the binding and interaction of various proteins or peptides to the lipids. Surface pressure/time experiments along with epifluorescence microscopy will investigate these interactions for each phosphoinositide monolayer highlighting the distinct properties of phosphoinositide/protein interactions.

Increasing the cell viability and heterologous protein expression of Pichia pastoris mutant deficient in PMR1 gene by culture condition optimization

In this study, we assessed the potential of PMR1-disrupted Pichia pastoris (Pppmr1) expressing human serum albumin and interferon alpha 2b fusion protein (HSA-IFN-alpha 2b) in large-scale fermentation. The high osmotic pressure of standard basal salts medium (BSM) was detrimental to the growth and viability of Pppmr1. HSA-IFN-alpha 2b was secreted into a supernatant with a concentration of up to 112 mg/L after 20 h of induction and then began to decline. In vitro stability tests indicated that the disappearance of HSA-IFN-alpha 2b was ascribed to proteolytic degradation. Decreasing the salt concentration of BSM medium to one quarter of the original formula improved the growth and viability of Pppmr1. As a result of reduced cell lysis and protease release, HSA-IFN-alpha 2b was stable in the supernatant, which enabled a longer production phase (30 h) and a higher expression level (215 mg/L). Lowering the culture temperature to 20 degrees C increased the cell viability during carbon source transition and alleviated the oxygen and methanol limitation, which extended the production phase to 40 h and increased the expression level to 680 mg/L. The addition of 2% Soytone prolonged the production phase to 60 h and increased the expression level to 1,260 mg/L, which was more than tenfold higher than that of Pppmr1 cultured under the conditions recommended by Invitrogen.

In Vitro Propagation of "Jarilla" (Larrea divaricata CAV.) and Secondary Metabolite Production

An efficient protocol for the in vitro germination and propagation of Larrea divaricata CAV. (Jarilla) was established. To determine the effect of different growth regulators on the growth rates and phenol production, apical-node microshoots from in vitro germinated plantlets were incubated on the following media: 1) full-strength MS (Murashige and Skoog) salt medium with different ratios of alpha-naphthaleneacetic acid (NAA) and N(6)-benzyladenine (BA); 2) after pre-treatment with indolebutyric acid (IBA), transfer to MS medium of different inorganic salt strengths; and 3) full-strength MS salt medium with different ratios of sucrose and IBA. Successful microshoot rooting percentages were achieved by the second and third strategies, the highest being 87.5-100%. The maximum principal shoot length and node number obtained by the second strategy corresponded to the plantlets previously induced with 50 microM IBA, and grown on half- or full-strength MS salt media (7.03+/-0.93 and 9.86+/-1.07 cm, respectively) while in the third strategy the most efficient micropropagation medium was full-strength MS salt medium supplemented with 7.5 microM IBA: 3% (w/v) sucrose (7.05+/-1.08 and 7.0+/-1.51 cm, respectively). The phenol concentration was determined by analytical HPLC. The highest content of nordihydroguiaretic acid (NDGA) accumulated in microplants of L. divaricata cultivated on half-strength MS salt medium (35.90+/-3.82 mg/g DW). Reducing the MS medium salt concentration by half, in the absence of IBA, it resulted in a higher NDGA production. NDGA production was not sensitive to the variation of IBA concentration. The medium supplemented with 5% (w/v) sucrose and 2.5 microM IBA induced not only a higher NDGA production but also a higher quercetin production.

Meio de cultura e tipo de explante no estabelecimento in vitro de espécies de maracujazeiro

O Brasil é um dos principais centros de dispersão da variabilidade genética do gênero Passiflora. Sua auto-incompatibilidade aliada à incidência de doenças do sistema radicular e da parte aérea, desmatamentos e monocultivos promovem perda de material genético. Tendo-se em vista o risco de erosão genética, torna-se necessário a conservação da variabilidade em bancos de germoplasma, de grande interesse no melhoramento de plantas. Estudos em relação ao tipo de explante e concentração dos meios de cultivo são necessários para se determinar protocolo de estabelecimento e conservação in vitro de germoplasma de maracujá. O objetivo deste trabalho foi avaliar a influência da concentração dos sais e nutrientes do meio MS e tipos de explantes no estabelecimento e crescimento das espécies de maracujazeiro Passiflora giberti N. E. Brown, P. edulis Sims e P. laurifolia L. Em cada espécie de Passiflora havia características próprias quanto ao desenvolvimento in vitro. O meio de cultura MS completo e os segmentos nodais que continham a segunda gema axilar tiveram melhores resultados em relação às demais.

Swelling of pH‐sensitive chitosan–poly(vinyl alcohol) hydrogels

AbstractThe swelling properties of different chitosan–poly(vinyl alcohol) (PVA) hydrogels were investigated as functions of the medium pH and salt concentration. The maximum swelling ability of the hydrogels was at a buffer pH of approximately 3, regardless of the PVA content in the hydrogels. The maximum mass of the swollen hydrogels was about 13 times that of their contracted counterparts. The cyclical swelling and contraction between pH 3 and pH 7 buffers and pH 3 and pH 3 buffers with salt confirmed the Donnan swelling mechanism of these hydrogels. The swelling mechanism was considered the transfer of water molecules driven by a concentration gradient. This was represented by a simplified mass‐balance model, which neglected the effect of the ionization reaction, for the initial swelling period. The effective mass‐transfer coefficient of water molecules during swelling, estimated with this model, gradually decreased with increasing PVA content in the hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4665–4671, 2006