Solubilizing Action Research Articles

Rizobactérias promotoras de crescimento de plantas isoladas de solos cultivados usando plantas Glycine max L. como isca

ABSTRACT: The current production of major crops, such as Glycine max L., has become increasingly adept on the use of bio-inputs, such as application of plant growth-promoting inocula. However, the evaluation of the potential of bacterial isolates from soils with different time histories of agricultural use are still scarce, and methods for isolation and testing of multifunctional microorganisms need to be continuously innovated and improved. Thus, we used G. max bait plants to attract rhizobacteria from soils obtained from three areas with different time histories of soybean cultivation. We evaluated the influence of the management and characteristics of soils on the phosphate-solubilizing bacterial population. We then tested the multifunctional potential of the isolated rhizobacteria for calcium phosphate (CaHPO4) and iron phosphate (FePO4) solubilization, considering their potential as microbial inoculants in the future. The use of bait plants enabled the isolation of 139 phosphate solubilizing rhizobacteria, including four strains with multifunctional potential. The largest number of solubilizing bacteria was obtained from the interaction of bait plants with soil from an area with a history of soybean cultivation for thirty consecutive years. The high concentration of P, Fe, and K found in the soil were associated with this occurrence. In the in vitro tests, the pH values of the culture media had a moderate negative relationship with the amounts of P made available by the isolates, indicating that other processes besides the availability of organic acids, may underlie the solubilizing action of the isolates. The rhizobacteria SAF9 (Brevibacillus sp.), SAF11 (Brevibacillus sp.), BRC11 (Pseudomonas fluorescens), and SAC36 (Bacillus velezensis) stood out as multifunctional and are indicated within a perspective of obtaining bioinoculants to promote plant growth directly, indirectly, or synergistically, contributing to increase the range of bio-inputs for soybean cultivation and more sustainable agricultural practices.

Salt Spray and Surfactants Induced Morphological, Physiological, and Biochemical Responses in Callistemon citrinus (Curtis) Plants

The growth and aesthetic value of ornamental plant species used near coastlines are negatively influenced by salt spray. The presence of surfactants could enhance salt damage. To analyze the influences of salt spray and surfactants alone and in combination with each other, individual Callistemon plants were subjected to different treatments for 8 weeks: a solution simulating the composition of seawater (salt spray), a solution containing an anionic surfactant (surfactant), a solution with salt spray and anionic surfactant (salt plus surfactants), and deionized water (control). To study the influence of different climatic conditions, two growing periods, from January to March (I CP) and from May to July (II CP), were established. Salt spray, alone or with surfactant action, influences plants’ growth and aesthetic features in different cycle periods. The percentage of leaf damage significantly increased with salt spray and salt plus surfactants during II CP (~27%). Additionally, the Na+ and Cl− contents were enhanced in the leaves in both CPs, but the contents in the roots were only enhanced in the II CP. The gas exchanges were significantly influenced by the treatments, especially during the II CP, when a reduction in net photosynthesis due to salt spray was observed starting from the second week of stress. At the end of the experiment, in both cycle periods, the leaf proline content increased in the salt spray and salt plus surfactants treatments. In both CPs, PCA revealed that the morphological and physiological parameters were directly associated with the control and surfactants treatments, whereas the mineral contents and biochemical parameters were directly correlated with the salt and salt plus surfactants treatments. The additive effect of surfactant stress, compared to salt stress, did not appear to be significant, with the exception of CP II, and for some parameters, the solubilization action of surfactants was favored by higher temperatures.

CULTIVATION OF ZUCCHINI (CUCURBITA PEPO L.) SUBMITTED TO NPK MINERAL FERTILIZATION AND SOIL CONDITIONING BACTERIA

Zucchini (Cucurbita pepo L.) has great socioeconomic importance for the Southeast and Center-South regions of Brazil, and can be cultivated throughout the Northeast region, especially in the state of Paraíba, due to its adaptability to the edaphoclimatic conditions of the Paraiba hinterland. The present study aimed to evaluate the growth of gas exchange and the production of the culture of zucchini (Cucurbita pepo L.) submitted to fertilization with NPK and soil conditioning bacteria. The experiment was in randomized blocks, with 10 treatments and 6 repetitions, the treatments corresponded to the combinations of NPK mineral fertilizer with doses of 0%, 50% and 100% of the need for culture and soil conditioning bacteria Azotobarvar® nitrogen fixing bacteria, Phosphatebarvar® bacteria phosphorus solubilizing action and Potabarvar® bacteria with potassium solubilizing action. T1 = Control (without mineral fertilizer and soil conditioning bacteria); T2 = with 100% of the mineral fertilizer recommended for the crop; T3 Azotobarvar® with the addition of 100% PK; T4 = Azotobarvar® with the addition of 50% nitrogen plus 100% PK; T5 = Potabarvar® with the addition of 100% NP; T6 = Potabarvar® with the addition of 50% potassium plus 100% NP; T7 = Phosphatebarvar® with the addition of 100% NK; T8 = Phosphatebarvar® with the addition of 50% phosphorus plus 100% NK; T9 = Azotobarvar®; Potabarvar®; Phosphatebarvar®; T10 = Azotobarvar®; Potabarvar®; Phosphatebarvar® with the addition of 50% NPK. The plants were grown in pots with a capacity of 45 dm3 for 49 days, during this period the plants were evaluated for growth, gas exchange, dry matter accumulation and production. The association of soil conditioning bacteria, with the 50% dose of NPK fertilization, promoted a greater number of fruits, production and height of the zucchini plants when compared to the treatment without inoculation of the bacteria. It was concluded that the highest values obtained for the growth and physiological parameters were observed in the treatments in which soil conditioning bacteria were used via seeds and fertigation.

CORN CULTIVATION (BRS 2022) SUBMITTED TO NPK MINERAL FERTILIZATION AND SOIL CONDITIONING BACTERIA

The corn crop is of great importance for Brazilian agriculture and can be influenced by several factors that interfere in the final productivity, among which the correct management of soil fertility stands out, carrying out a correct fertilization to achieve a high yield. The objective of this work was to evaluate the development and productivity of maize subjected to different doses of phosphorus, potassium and nitrogen, constant, and to evaluate the effect of inoculating seeds with phosphorus and potassium solubilizing and N-fixing bacteria. conducted in the experimental area of the Center for Agricultural Sciences at the Federal University of Campina Grande (UFCG) (CCTA), in – PB. The experiment was in randomized blocks, with 10 treatments and 6 replications, the treatments corresponded to the combinations of NPK mineral fertilizer with doses of 0%, 50% and 100% of the crop need and soil conditioning bacteria AzotoBarvar-1® fixing bacteria nitrogen, PhosphoBarvar-2® bacteria with phosphorus solubilizing action and PotaBarvar-2® bacteria with potassium solubilizing action. T1 = Control (without mineral fertilizer and soil conditioning bacteria); T2 = with 100% of the mineral fertilizer recommended for the crop; T3 AzotoBarvar-1® with addition of 100% PK; T4 = AzotoBarvar-1® with addition of 50% nitrogen plus 100% PK; T5 = PotaBarvar-2® with addition of 100% NP; T6 = PotaBarvar-2® with addition of 50% potassium plus 100% NP; T7 = PhosphoBarvar-2® with addition of 100% NK; T8 = PhosphoBarvar-2® with addition of 50% phosphorus plus 100% NK; T9= Nitrogen Barvar-2®; PotaBarvar-2®; PhosphoBarvar-2®; T10= Nitrogen Barvar-1®; PotaBarvar-2®; PhosphoBarvar-2® with addition of 50% NPK. Plants were grown in pots with a capacity of 45 dm3 for 59 days, mean plant height (ALP) and leaf length (CF) 28 days after plant emergence and Leaf number (NF) 5 days after emergence of plants submitted to NPK fertilization and soil conditioning bacteria, 49 days after germination. Where there was interaction between treatment and cultivar. During this period, the plants were evaluated for growth, dry matter accumulation and production. The association of soil conditioning bacteria, with a dose of 50% fertilization with NPK, which promoted greater ear size, production and height of maize plants when compared to the treatment without bacterial inoculation. It is concluded that the highest values obtained for the growth and physiological parameters were observed in the treatments in which the soil conditioning bacteria via seeds and fertigation were used.

INTERACTION OF 3-HYDROXY PYRIDINE AND SURFACTANT MICELLES: A FLUORESCENCE STUDIES

Objective: Micellar solubilization is a powerful alternative for dissolving hydrophobic compound in aqueous environment. 3-hydroxy pyridine (3- HP) derivatives are the potential endogenous photosensitizers. 3-HP derivatives show protective effect in clinical extreme condition such as hypoxia, hyperthermia, hypokinesia. Micellization of 3-HP followed by solubilization would catalyze its pharmaceutical activities which may serve better results in medicinal and analytical fields. Methods: Fluorescence and absorption spectroscopy techniques are used to monitor the micellar solubilization studies of 3-HP. Solubilization studies of 3-HP with various anionic, cationic and nonionic surfactants have been performed in aqueous medium around 23–25°C temperature. The solubilization action of the surfactant has also been determined by theoretical calculated spectral parameters such as empirical fluorescence coefficient, quantum yield, stokes, shift and molar absorption coefficient. Results: 3-HP shows fluorescence excitation peak at 315 nm and emission peak at 390 nm respectively while the absorbance of 3-HP has been found to be maximum at 305 nm. The fluorescence as well as the theoretically calculated spectral data has been used to characterize the hetero environment of the micelles in terms of their polarity, probe solubilization site and critical micelle concentration. Conclusion: This article briefly discusses the importance of surfactants in biological system model as well as the use of micelles in pharmacy as an important tool that finds numerous applications.

Biocompatible supramolecular systems based on novel cationic imidazolium- and urethane-containing amphiphiles: Self-assembly and antimicrobial properties

In the framework of this investigation novel cationic amphiphiles of N-(2-butylaminocarbonyloxyethyl)-N-alkylimidazolium bromides series have been synthesized and characterized in terms of their aggregation capacity in aqueous solutions, antimicrobial properties and solubilization action toward hydrophobic dye. Using tensiometry, conductometry and fluorescence spectroscopy techniques it has been demonstrated, that the presence of urethane fragment with butyl moiety is responsible for the one order of magnitude decrease of critical micelle concentration of amphiphiles in comparison with unsubstituted analogs. Fabrication of aggregates with hydrodynamic diameter in the range of 4–10 nm has been exhibited for all amphiphiles. Transmission electron microscopy technique allows to establish the spherical shape of aggregates formed. These amphiphiles were shown as effective solubilizers of hydrophobic azodye, which efficacy could be 2.5-fold increased by elongation of the length of hydrophobic tail by four methylene units. Estimation of interaction of amphiphiles with biological objects has revealed, that all compounds exhibit high bacteriostatic and bactericide properties preferably toward gram-positive strains, as well as they have low hemolytic activity at active concentrations. Antibacterial properties of tetradecyl amphiphilic derivative have surpassed norfloxacin by 5 and 8.5 times in relation to Staphylococcus aureus and Bacillus cereus, respectively.

Hydroxypropyl β‐Cyclodextrin Solubilizing Hydrophobic Initiator to Initiate Copper‐Mediated RDRP of NIPAM in Aqueous Media

AbstractThe copper mediated reversible deactivation radical polymerization (Cu0‐RDRP) can realize the precise synthesis of vinyl polymers in aqueous media. To our best of knowledge, there are few hydrophobic initiators directly utilized to perform the aqueous Cu0‐RDRP because the heterogeneity usually causes the polymerization to go out of control. This article first describes a very small number of hydroxylpropyl β‐cyclodextrins (HP‐β‐CDs) enabling to solubilize a bifunctional hydrophobic initiator tetraethylene glycol bis(2‐bromoisobutyrate) (T2B) into water to initiate the homogeneous Cu0‐RDRP of N‐isopropylacrylamide (NIPAM) giving rise to well‐defined poly(N‐isopropylacrylamide) (PNIPAM). The solubilization action is arisen from the inclusion complexation of HP‐β‐CDs with T2B as evidenced by 2D NOESY and 2D DOSY NMR analyses. Furthermore these entrapped HP‐β‐CDs show little effect on the polymerization process as they all skip off the initiator at the very beginning of the polymerization as determined by GPC and 1H NMR measurements.

Effect of cyclodextrin complexation on solubility of novel anti-Alzheimer 1,2,4-thiadiazole derivative

New 1,2,4-thiadiazole derivative displaying neuroprotective potential and high activity in the treatment of Alzheimer’s disease has been synthesized. The objective of this study was to improve the aqueous solubility of this drug-like compound by means of complex formation with native and hydroxypropylated β-cyclodextrins. To this end, aqueous solubility of 1,2,4-thiadiazole derivative was investigated in the presence of β-cyclodextrins. It was shown that the phase solubility diagrams are of Bs type demonstrating the initial increase in thiadiazole solubility in solutions of cyclodextrins (concentration up to 0.01 mol kg−1) followed by a solubility decrease due to the precipitation of the complexes formed. In comparison with β-cyclodextrin, hydroxypropyl-β-cyclodextrin displays more pronounced solubilizing action since it forms more stable complexes with thiadiazole. Solid complexes of 1,2,4-thiadiazole derivative with β-cyclodextrins were prepared by grinding and freeze-drying methods. DSC, TG, hot-stage microscopy, solid-state 13C MAS CP/TOSS NMR, powder X-ray diffractometry and FTIR spectroscopy were used to prove the existence of complexes in the solid state. Solubility of the obtained formulations was also examined. It was found that complexes of thiadiazole with hydroxypropyl-β-cyclodextrin exhibited higher solubility in phosphate buffer (pH 7.4) compared with pure thiadiazole and its complexes with β-cyclodextrin.

Solubility enhancement of gluten and organic compounds by arginine

Arginine suppresses protein–protein and protein–surface interactions and thus is expected to increase the solubility of the proteins. We have examined here the effects of arginine on the solubility of a highly insoluble protein, gluten, and two organic compounds, octyl-gallate and coumarin, which have low to moderate aqueous solubilities. Arginine significantly increased the solubility of these molecules concentration dependently, while a weak salting-out salt, NaCl, decreased it. The observed ability of arginine to salt-in these compounds can be explained from its binding to aromatic groups and protein surface. Such solubilizing action of arginine may be used to enhance the solubility of poorly soluble organic drug substances.

Solubilization of poorly soluble calcium salts of organic acids with sorbitol

Computer simulation was used to demonstrate the formation of complexes between calcium cations and calcium succinate (CS) with sorbitol in an aqueous environment. Solubility-associated descriptors of complexes were calculated, i.e., the enthalpies of complex formation and hydration and log P. Experimental data supported the theoretical calculations in terms of measurements of the solubility of calcium succinate, citrate, and malate in solutions of sorbitol at different concentrations. Aqueous sorbitol was shown to have a solubilizing action in relation to these salts. These results allowed development of a pediatric syrup containing CS in a combined sorbitol-fructose base.

Quantitative Analysis of the Solubilizing Action of MTAD, Sodium Hypochlorite, and EDTA on Bovine Pulp and Dentin

Necrotic bovine pulp and dentin were used in this study as model tissues to represent the organic and inorganic components of the smear layer present in instrumented root canals. The capabilities of endodontic irrigants to dissolve pulverized forms of these tissues were compared. Lyophilized tissue samples were mixed for 2 h at 37 degrees C with MTAD, three concentrations of sodium hypochlorite (NaOCl), 17% EDTA, or isotonic saline. Undissolved tissues were rinsed with water and lyophilized. The change in tissue weight after exposure to an irrigant was measured to quantify solubilization. The results showed that various concentrations of NaOCl removed organic components of pulp and dentin effectively. As pulp solubilizers 5.25% and 2.60% NaOCl were equal (>90%), and 5.25% NaOCl was capable of dissolving virtually the entire organic component of dentin. EDTA was capable of solubilizing inorganic material in dentin and organic material in pulp and likely also in dentin. It dissolved >70% of the dentin and >51% of the pulp. The solubilizing effects of MTAD on pulp and dentin were somewhat similar to those of EDTA. The major difference between the actions of these solutions was a high binding affinity of doxycycline present in MTAD for the dentin.

Solubilization of tenoxicam via different techniques

In this study, several techniques were employed to improve the aq. soly. of tenoxicam. These techniques include co-​solvency, micellar solubilization and solid dispersions using different water-​sol. polymers. The aq. soly. of tenoxicam in presence of 10​% of formamide, DMF and DMSO was enhanced about 4.5, 3.1 and 2.8 times, resp. In addn., the results show that the hydroxylated cosolvents (glycerol, PG, PPG, PEG 200, PEG 300, PEG 400 and PEG 600) just potentiated the aq. soly. of the drug. Several classes of non-​ionic surfactants were studied for their solubilizing action on tenoxicam. These classes were polysorbates (Tweens)​, polyoxyethylene alkylethers (Brijs) and polyoxyethylene stearates (Myrjs)​. Tween 80 exhibited a better solubilizing capacity on tenoxicam than other investigated tweens and they could be arranged according to their solubilizing capacity on the drug and the distribution coeff. of the drug between their micelles as: Tween 80 > Tween 60 > Tween 40. It is clearly evident that the solubilizing effect of these micellar forming agents increases as the hydrophobic chain length of the surfactant increases. In addn., Brij 35 exhibited a higher solubilizing capacity on the drug than Brij 58. Furthermore, Myrj 59 exhibited higher solubilizing power on tenoxicam compared to Myrj 53 and Myrj 52. These results indicate the relationship between the aq. soly. of the drug in presence of the above tested surfactants and its distribution coeff. between micellar and aq. phases. The dissoln. rate of tenoxicam in presence of PEG 4000 and PVP 40000 in its solid dispersions was improved esp. with PVP 40000 (in a drug: polymer ratio 1:9)​. IR, DSC and x-​ray diffraction studies were conducted to investigate the mechanism responsible for this improvement

Interaction of the glycoprotein excreted by Pseudoalteromonas antarctica NF 3 with phosphatidylcholine liposomes

The ability of an exopolymer of glycoproteic character (GP) excreted by a new gram-negative specie, Pseudoalteromonas antarctica NF 3, to coat phosphatidylcholine (PC) unilamellar liposomes and to protect these bilayer structures against the solubilizing action of the non-ionic surfactant Triton X-100 (T X-100) has been investigated. TEM micrographs of freeze fractured liposome/GP aggregates reveal that the presence of GP in liposome suspensions resulted in the formation of a continuous thin film that coated tightly these bilayer structures. The complete coating of these vesicles was already achieved at a PC:GP weight ratio of about 9:1. Higher GP amounts (up to a PC:GP weight ratio of 1:1) led to a progressive growth of this film which exhibited at the highest GP proportion a multilayered structure. An increasing resistance of PC liposomes to be solubilized by T X-100 took place as the proportion of GP in the system rose, although this protective effect was more effective at low GP proportions (PC:GP weight ratios from 9:1 to 4:1). Thus, although in the range of PC:GP weight ratios from 9:1 to 6:4 a direct dependence was found between the growing of the covering structure and the resistance of the coated liposomes to be solubilized by T X-100, the best protection effect occurred when this covering structure was a thin and continuous film with a thickness not higher than 15–20 nm (PC:GP weight ratios ranging from 9:1 to 4:1).

Adsorption on γ-aluminium oxide from a multicomponent aqueous solution. Effect of cosolvent, concentration, temperature, pH and substrate surface porosity

A model aqueous metal working fluid was used to investigate the applicability of current models of aqueous surfactant systems for the interpretation of observed effects on variations in different parameters on adsorption from a complex mixture. The base composition consists of nonanoic acid, N-butyl- N, N-diethanol amine, dodecanol and varying proportions of diethyleneglycol monobutylether and water. Experiments were performed at concentrations for the base composition close to maximum surface coverage. Results demonstrate the detrimental effect of high concentrations of a solubilizing component on adsorption. Adsorption is found to be suppressed even for the acid in the presence of cosolvent, despite an observed lowering of solution pH, which would be expected to favour anion adsorption. It is inferred, from experimental values of adsorption-desorption ratios and relative cosolvent affinity for the aluminium oxide surface, that extensive use of hydrogen-bonding possibilities is needed in order for the molecule to attach to the solid surface. It seems that the effect exerted by the cosolvent on the adsorption of other components is the result of a solubilizing action rather than competitive displacement. Dilution studies show prominent component adsorption maxima. The position of maximum adsorption depends on component type and concentration of cosolvent in the base fluid. Adsorption of the anionic component is promoted by a lowering of solution pH as expected, while dodecanol adsorption is suppressed, possibly as a result of competitive conditions. Temperature variation effects on adsorbed amounts show that anionic surfactant adsorption is promoted, while dodecanol and amine counter-ion adsorption is suppressed by a temperature increase. Temperature variation data for a simple affinity function show linear fits in van't Hoff type plots, and this is taken to indicate concentration-independent differential adsorption enthalpies close to maximum surface coverage. A nonlinear fit for the amine is suggested to depend on temperature-dependent proton dissociation equilibrium and to indicate that this species is adsorbed mainly as a cation. From a comparative study of the effect of substrate porosity it is concluded that the present system is adsorbed to form a bilayer with an average molecular parking area of 30 Å 2 in each layer and that a substantial portion of the microporous area is not available for adsorption under the chosen experimental conditions, probably due to blocking up of crevice-like channels by initial adsorption.

Characterization of a diflunisal polyethylene glycol solid dispersion system

This work involves the study of the nature of a possible interaction of diflunisal and polyethylene glylol (PEG) in solution and the solid state. Dynamic and equilibrium solubility studies, solvent power calculation and heat of solution determination were used to elucidate the mechanism of interaction in solution. Differential scanning calorimetric studies, infrared spectroscopy and hot stage microscopy were used to elucidate the mechanism of interaction in the solid state. From these studies it was concluded that no chemical interaction takes place between diflunisal and PEG neither in solution nor in the solid state. The increased solubility of diflunisal when dispersed in PEG could be attributed to one or more of several factors such as local solubilization action, reduction in particle size of the drug, alteration of the surface characteristics of the drug particles, increased thermodynamic activity and the high affinity of the drug to the polymer solution.

Studies on the mechanism of cholesterol uptake and on the effects of bile salts on this uptake by brush-border membranes isolated from rabbit small intestine

The effect of bile salts and other surfactants on the rate of incorporation of cholesterol into isolated brush-border membranes was tested. At constant cholesterol concentration, a stimulatory effect of taurocholate was noticed which increased as the bile salt concentration was raised to 20 mM. Taurodeoxycholate was as effective as taurocholate at concentrations of up to 5 mM and inhibited at higher concentrations. Glycocholate was only moderately stimulatory whereas cholate was nearly as effective as taurocholate at concentrations above 5 mM. Other surfactants such as sodium lauryl sulfate and Triton X-100 were very inhibitory at all concentrations tried whereas cetyltrimethyl ammonium chloride was stimulatory only at a very low range of concentrations. These micellizing agents all caused some disruption of the membranes and the greater effectiveness of taurocholate in stimulating sterol uptake was partly relatable to the weaker membrane solubilizing action of this bile salt. Preincubation of membranes with 20 mM taurocholate followed by washing and exposure to cholesterol-containing lipid suspensions lacking bile salt, did not enhance the incorporation of the sterol. In the absence of bile salt the incorporation of cholesterol was unaffected by stirring of the incubation mixtures. Increasing the cholesterol concentration in the mixed micelle while keeping the concentration of bile salt constant caused an increase in rate of sterol incorporation. This increased rate was seen whether the cholesterol suspension was turbid, i.e., contained non-micellized cholesterol, or whether it was optically-clear and contained only monomers and micelles. When the concentration of taurocholate and cholesterol were increased simultaneously such that the concentration ratio of these two components was kept constant, there resulted a corresponding increase in rate of cholesterol uptake. The initial rates of cholesterol incorporation from suspensions containing micellar and monomer forms of cholesterol were much larger than from solutions containing only monomers of the same concentration. The rates of incorporation of cholesterol and phosphatidylethanolamine from mixed micelles containing these lipids in equimolar concentrations were very different. The results as a whole suggest at least for those experimental conditions specified in this study, that uptake of cholesterol by isolated brush-border membranes involves both the monomer and micellar phases of the bulk lipid and that the interaction of the micelles with membrane does not likely involve a fusion process.

Correlation of Dielectric Constant and Solubilizing Properties of Tetramethyldicarboxamides

The dielectric constants of aqueous solutions of four tetramethyldicarboxamides (tetramethylpimelamide, tetramethylsuberamide, tetramethylazelamide, and tetramethylsebacamide) were measured at 25°. The values obtained were utilized in assessing the solubility behavior patterns of glutethimide, a semipolar, water‐insoluble drug in these amide‐water systems. At equimolar concentrations of water‐rich amide solutions, the solubilizing power paralleled the chain length of the amides. The higher homologs appeared to favor more extensive solvation, as shown by the lower dielectric constants of their resulting solutions. Deviation in solubilizing action between the odd‐carbon amides and the even‐carbon amides, however, was exhibited at higher amide concentrations. The two odd‐carbon amides, tetramethylpimelamide and tetramethylazelamide, showed consistently greater solubilizing action. This phenomenon was attributed to the greater association tendencies of the odd‐carbon amides with water, which effectively reduced self‐associations of glutethimide.

ALTERAÇÕES MICROBIANAS EM ROCHAS: SOLUBILIZAÇÃO DO FERRO POR AÇÃO DE FUNGOS EM DIABÁSIOS

Experimental attack on a mafic rock by a liquid culture of an Aspergillus niger strain isolated from soil, which exhibited a striking solubilizing action upon its iron-containing minerals, was investigated. After 25 days, the iron content of the fungal solutions was 26 times higher than in the sterile control flasks. The microbiological activity was followed by the dry weight of the mycelium, the glucose consumption, the evolution of the total acidity, and the pH value of the cultures. The kinetics of the iron solubilization of the mycelial growth and the metabolic activity showed significant relationships. The mycelial growth was improved by the presence of the cations extracted from the rock samples. The solubility of iron in these minerals depended on their nature, the surface of attack, and the concentration of the metabolic products; probably all three. Formation of complex could be the mechanism involved, considering that a strong cation exchange-resin was not able to extract iron from the culture solutions.

Effect of additives on deposit formation in engines

1. The ability of additives to ameliorate the severe formation of carbonaceous deposits on diesel-engine pistons is related to their solubilizing action with respect to oxidation products. 2. A characteristic feature of the conditions to which oils are exposed in engine operation is the presence of increased amounts of dissolved water in the oil. Hence, the most effective additives in reducing carbon deposit formation are those for which the solubilizing action is improved by the presence of moisture. 3. The antideposition properties of additives and additive packages can be evaluated from their effects on the dispersant-stabilizing capability of a water-contaminated standard used oil.

Study of interaction between succinimides and bisphenols by PMR

STUDIES of the compositions of detergent and anti-oxidizing additives confirm that in many cases a synergetic effect is observed on combining these additives which is particularly clear when determining the solubilizing action of additives [1-3]. An I R spectroscopic study of the interaction between suceinimides and bisphenols (and zinc dithiophosphates) indicates [4] that the interaction between the components of mixtures investigated is accompanied by the formation of hydrogen bonds which, apparently, results in a certain modification of the structure of associates (micelles) formed; this is, in all probability, the cause ()f synergism observed on combining these additives. The interaction between succinimides and bisphenols was studied by PMR. The presence of active proton-donor and proton-aeceptor ~ o u p s in the additives studied were a prerequisite for selecting this method. Proton magnetic resonance spectra were obtained using a JNM-C-60HLC high resolution PMR spectrometer and an operating frequency of 60 MHz. Chemical displacements in scale /i were measured in relation to hexamethyldisiloxane (internal standard). Chemically pure CC14 was used as solvent. The type of interaction between the additives examined can be evaluated from the variation of chemical shifts, line intensity and width and from the variation in the configuration of peaks in the spectra. Seven industrial suceinimide type additives were used in the form of 50% solutions in a paraffin-naphthene oil free from aromatics. The additives stu= died in order of increase of suceinimide molecular weight are as follows: