Low Concentrations Of Acetic Acid Research Articles

Empirical equation of CO2 corrosion with presence of low concentrations of acetic acid under turbulent flow conditions

The presence of organic acid species in formation water of oil and gas reservoirs has long been suspected to contribute to the corrosivity of CO2 corrosion. The effect had been regarded as secondary until new findings in the 1980s and 1990s revealed the increase in corrosion rate in CO2 environment with the presence of acetic acid species. This is potentially detrimental as most of the predictive models used in corrosivity assessment of the field do not incorporate considerations of the effects of acetic acid species. This paper presents experimental corrosion rates of carbon steel in CO2 environments with the presence of low concentrations of acetic acid species under the turbulent flow conditions, based on linear polarisation resistance analysis. The experimental corrosion rates are compared with the corrosion rates predicted by industrial predictive models such as Norsok and Cassandra. Based on the findings, the authors can conclude that acetic acid species increase the corrosion rate of carbon steel in CO2 corrosion and standard predictive models do not capture this effect. An empirical equation is proposed to cater for the presence of low concentrations of acetic acid in CO2 corrosion under turbulent conditions.

Gastrointestinal dysmotility is associated with altered gut flora and septic mortality in patients with severe systemic inflammatory response syndrome: a preliminary study

The gut is an important target organ for injury after severe insult, and resolution of feeding intolerance is crucial for critically ill patients. We investigated gut flora and motility to evaluate the impact of gastrointestinal dysmotility on septic complications in patients with severe systemic inflammatory response syndrome (SIRS). Sixty-three ICU patients with severe SIRS were divided into two groups depending on their intestinal condition. Patients with feeding intolerance comprised patients who had feeding intolerance, defined as ≥ 300 mL reflux from nasal gastric feeding tube in 24 h, and patients without feeding intolerance comprised patients with no feeding intolerance. We compared fecal microflora, incidences of bacteremia, and mortality between these groups. Analysis of feces showed that patients with feeding intolerance had significantly lower numbers of total obligate anaerobes including Bacteroidaceae and Bifidobacterium, higher numbers of Staphylococcus, lower concentrations of acetic acid and propionic acid, and higher concentrations of succinic acid and lactic acid than those in patients without feeding intolerance (P ≤ 0.05). Patients with feeding intolerance had higher incidences of bacteremia (86%vs 18%) and mortality (64%vs 20%) than did patients without feeding intolerance (P ≤ 0.05). Gut flora and organic acids were significantly altered in patients with severe SIRS complicated by gastrointestinal dysmotility, which was associated with higher septic mortality in SIRS patients.

Production of schizophyllan glucan by Schizophyllum commune ATCC 38548 from detoxificated hydrolysate of rice hull

Production of schizophyllan glucan (bioflocculant) of Schizophyllum commune using the activated charcoal detoxificated rice hull hydrolysate was investigated and established in this study. Results indicated S. commune was highly sensitive to furfural and sodium ions; however, supplementation of acetic acid (0.5 g/L) to media could improve the tolerance of S. commune to sodium ions. Two folds of enhancement of the product yield achieved when the optimal detoxificated hydrolysate treated with calcium dioxide was used as compared to that of the NaOH-neutralized hydrolysate. Bioflocculant production reached 1.30 g/L in the optimal detoxificated hydrolysate after 16 days of cultivation with a 2.8-fold enhancement as compared to that of the hydrolysate without detoxification. The study firstly demonstrated the feasibility of using the activated charcoal detoxificated rice hull hydrolysate for schizophyllan production by S. commune. And, the influence of individual or combined inhibitors of rice hull hydrolyate on the growth and product formation of S. commune was clarified. Low concentrations of acetic acid could diminish the inhibition of combined inhibitors under a high salt concentration.

Microwave assisted acid cleavage for denaturation and proteolysis of intact human adenovirus

Microwave assisted acid cleavage was applied directly to intact adenovirus type 5 to achieve denaturation and proteolysis in a single reaction. The speed of the digestion, coupled with the simplicity of MALDI analysis, allowed peptide products to be profiled in less than 5 min. Identification of peptides from a range of proteins by MALDI-TOF confirms that both denaturation and proteolysis were achieved using low concentrations of acetic acid (12.5%) and short incubations (1.5–2 min) at high temperatures (140 °C). These conditions favor production of peptides that carry Asp on their C-termini. When this cleavage reaction is carried out in highly enriched H 2 18O, a single atom of 18O is introduced site-specifically into the carboxyl terminal. The labeling reaction is applied to label reporter peptides from human adenovirus type 5 harvested from HeLa cells. Small peptide products of endogenous processing were also observed.

Volatile organic acid adsorption and cation dissociation by porphyritic andesite for enhancing hydrolysis and acidogenesis of solid food wastes

Volatile organic acid adsorption, cation dissociation by porphyritic andesite, and their effects on the hydrolysis and acidogenesis of solid food wastes were evaluated through batch experiments. The acetic acid adsorption experiments show that pH was mainly regulated by H + adsorption. The mono-layer and multi-layer adsorption were found under the low (8.3–83.2 mmol/L) and high (133.22–532.89 mmol/L) initial acetic acid concentration, respectively. The dissociated cations concentration in acidic solution showed the predominance of Ca 2+. Porphyritic andesite addition elevated the pH levels and accelerated hydrolysis and acidogenesis in the batch fermentation experiment. Leachate of porphyritic andesite addition achieved the highest hydrolysis constant of 22.1 × 10 −3 kg m −2 d −1 and VS degradation rates of 3.9 g L −1 d −1. The highest activity of microorganisms represented by specific growth rate of ATP, 0.16 d −1, and specific consumption rate of Ca 2+, 0.18 d −1, was obtained by adding leachate of porphyritic andesite.

Improved 2,3-butanediol production from corncob acid hydrolysate by fed-batch fermentation using Klebsiella oxytoca

Corncob acid hydrolysate, detoxed by sequently boiling, overliming and activated charcoal adsorption, was used for 2,3-butanediol production by Klebsiella oxytoca ACCC 10370. The effects of acetate in hydrolysate and pH on 2,3-butanediol production were investigated. It was found that acetic acid in hydrolysate inhibited the growth of K. oxytoca while benefited the 2,3-butanediol yield. With the increase in acetic acid concentration in medium from 0 to 4 g/l, the lag phase was prolonged and the specific growth rate decreased. The acetic acid inhibition on cell growth can be alleviated by adjusting pH to 6.3 prior to fermentation and a substrate fed-batch strategy with a low initial acetic acid concentration. Under the optimum condition, a maximal 2,3-butanediol concentration of 35.7 g/l was obtained after 60 h of fed-batch fermentation, giving a yield of 0.5 g/g reducing sugar and a productivity of 0.59 g/h l.

Effect of acetic acid deamidation‐induced modification on functional and nutritional properties and conformation of wheat gluten

Acids are often used for deamidating proteins, but the literature on acetic acid deamidation of proteins is sparse. Previous research on acetic acid-induced modification of proteins has focused on peptide proteolysis by relatively high concentrations of acetic acid (>1.5 mol L(-1)) rather than on the accompanying effect of deamidation. Therefore the objective of this study was to determine the deamidation effect of acetic acid with as little peptide proteolysis as possible by employing low-concentration acetic acid (<0.05 mol L(-1)) to deamidate wheat gluten. Changes in surface hydrophobicity, conformation, functional properties and nutritional characteristics of acetic acid-modified samples were determined and compared with those of hydrochloric acid (HCl)-modified samples. At similar degree of deamidation and nitrogen solubility index, samples deamidated with acetic acid showed less destruction of peptides bandings, better foaming properties and a more decompacted form (lower S--S content in protein as determined by Raman spectroscopy) than those deamidated with HCl and also exhibited improved emulsification capacity and emulsion stability compared with native wheat gluten. Acetic acid deamidation led to fewer changes in peptide molecular size and secondary structure of wheat gluten compared with HCl deamidation according to the results of sodium dodecyl sulfate polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy respectively. Amino acid analysis revealed that the nutritional characteristics of wheat gluten were well maintained after deamidation with acetic acid. The results show that low-concentration acetic acid can modify wheat gluten mainly by deamidation, resulting in deamidated wheat gluten with good functional and nutritional properties.

Imaging of epithelial tissue in vivo based on excitation of multiple endogenous nonlinear optical signals

We demonstrate an integrated optical microscope to image the living epithelial tissue by simultaneously exciting multiple endogenous nonlinear optical signals. By employing the spectral lifetime detection capability, this technology provides a unique approach to sensing the fine structure, the protein distribution, and the cellular metabolism of epithelial tissue in vivo. In particular, we investigated the two-photon excitation fluorescence (TPEF) of tryptophan, an essential amino acid serving as the building block of protein. Our findings show that the TPEF of cellular tryptophan produces a good contrast to reveal the morphology of the epithelial cell layer, and the contrast can be further enhanced by applying low-concentration acetic acid.

Evaluation of the efficacy of disinfection procedures against Burkholderia cenocepacia biofilms

In the present study we evaluated the efficacy of various procedures recommended for the disinfection of respiratory equipment and other materials in cystic fibrosis, using both planktonic and sessile Burkholderia cenocepacia cells. A modified European Suspension Test was performed to determine the effects of the disinfection procedures on planktonic cells. The ability of the treatments to kill sessile cells and to remove biofilm biomass was evaluated using two resazurin-based viability assays and a crystal violet staining on biofilms grown and treated in 96-well microtitre plates. The effect of chlorhexidine and hydrogen peroxide treatments on the viability of sessile B. cenocepacia cells was clearly reduced compared to the effects on planktonic cells. Treatments with low concentrations of sodium hypochlorite (0.05%, 5 min) and acetic acid (1.25%, 15 min) also resulted in insufficient reductions in the number of viable sessile cells. There was no relation between the ability of the disinfectants to remove biofilm biomass and their potential to kill biofilm cells. In conclusion, our study indicates that testing of the efficacy of disinfectants should be performed on both planktonic and sessile cells, with particular attention to their effects on cellular viability.

Comparative Analysis of Genetically Modified Yeasts in Winemaking

These days there are many dilemmas about perspectivity of GMO application. Not only economics, legislation and public opinion, but also technological properties of each GMO are very important and should be analysed and evaluated. SWOT analysis, analysis of attractivity and competitive ability and survey of Slovenian oenologist opinions were conducted about current technology regarding GMOs in winemaking. We found that the most important and interesting GMOs, in the opinion of oenologists, are yeast with enhanced production of glycerol and malolactic yeast, the last already approved as GRAS by the United States FDA. The market attractivity and competitive ability analysis in Slovenian circumstances showed us that the most important GMOs in the future will be yeasts capable of releasing terpenoids, but also very important are malolactic yeasts and yeasts producing higher concentration of glycerol and lower concentration of acetic acid.

Inhibitory effects of nicorandil, a KATP channel opener and a nitric oxide donor, on overactive bladder in animal models

To investigate the effects of nicorandil, an ATP-sensitive potassium (K(ATP)) channel opener with a nitric oxide (NO) donor property, on overactive bladder (OAB) in animal models. Nicorandil is currently used clinically to treat ischaemic heart disease. Three animal OAB models were used: (i) C-fibre mediated bladder overactivity by infusion of a low concentration of acetic acid (AA) into the bladder in female Wistar rats; (ii) bladder outlet obstruction (BOO) created by partial urethral obstruction in female Wistar rats; and (iii) neuronal NO synthase (nNOS) knockout (KO) mice with urinary frequency. The effects of nicorandil and KRN2391, both of which act as K(ATP) channel openers and NO donors, on the OAB models were examined. Cystometry showed that intravesical instillation of nicorandil and KRN2391 successfully inhibited OAB induced by intravesical instillation of AA. In the BOO model compared with untreated BOO rats, both nicorandil (1 and 3 mg/kg, orally) and KRN2391 (1 mg/kg, orally) significantly reduced the voiding frequency. Compared with wild-type mice, nNOS KO mice had urinary frequency with no change in the total urine volume. Nicorandil (3 mg/kg, orally) and KRN2391 (1 mg/kg, orally) significantly reduced the voiding frequency in nNOS KO mice. Our in vivo results show that nicorandil, a K(ATP) channel opener with a NO donor property, can suppress OAB from both neurogenic and myogenic causes. Nicorandil appears to be a promising candidate for clinical use in patients with OAB.

The effect of moisture level on high-moisture maize ( Zea mays L.) under hermetic storage conditions— in vitro studies

Under humid and warm conditions harvested grains are susceptible to molding and rapid deterioration. Therefore, they should be dried to safe moisture levels that inhibit the activity of microorganisms. Drying to these moisture levels is not economical for farmers in developing countries. Preservation of grains at intermediate moisture levels under hermetic storage conditions could be feasible and economical in warm and moist climates. The purpose of the current study was to examine the effect of various moisture contents (m.c.) on the quality of maize grains in self-regulated modified atmospheres during hermetic storage. Maize at 14, 16, 18, 20 and 22% m.c. was initially conditioned for 28 days in tightly wrapped plastic bags and then stored in sealed containers at 30 °C for up to 75 days. Carbon dioxide produced within the containers replaced the oxygen. As the m.c. increased the time for O 2 depletion shortened, from 600 h at 14% m.c. to 12 h at 22%. The maize at 20 and 22% m.c. exhibited the highest dry matter (DM) losses, the lowest germination rates and the highest yeast and bacteria counts. The major fermentation product in the hermetically sealed maize was ethanol (0–5 g kg −1 DM), along with lower concentrations of acetic acid (0–1 g kg −1 DM). The results obtained from the in vitro experiments indicate that maize at the tested moisture levels can be stored satisfactorily under sealed conditions in which self-regulated atmospheres provide protection against microflora damage. Further large-scale trials will be needed to evaluate the economic feasibility of storing high-moisture maize.

Aerobic liquid-phase oxidation of p-xylene over metalloporphyrins

The five metalloporphyrins ( T (p- Cl ) PPM , M = Fe , Mn , Co , Cu , Zn ) with different metal nuclei were synthesized, and their catalytic aerobic liquid-phase oxidations of p-xylene into p-toluic acid, p-toluic aldehyde and terephthalic acid using a low concentration of acetic acid as solvent without any halide additives, were studied. The p-xylene conversions and the oxidation product distributions were found to be affected by the structures and concentration of the metalloporphyrins as well as the reaction parameters such as time, temperature and air pressure. The formation of some intermediate oxidation products in the oxidation process also influenced the reaction conversions and the product distribution. Among the metalloporphyrins used, tetrakis(p-chlorophenylporphinato)manganese chloride ( T (p- Cl ) PPMnCl ) was the most efficient catalyst for the oxidation of p-xylene. Under the conditions of 180 °C and 2.0 MPa, 44% conversion of p-xylene and 85% selectivity of p-toluic acid were obtained. Based on the results obtained, a preliminary mechanism of the oxidation of p-xylene over metalloporphyrins was proposed.

Influence of molasses additive and moisture level at ensiling on fermentative characteristics of Panicum maximum

Silages made from directly cut or wilted Panicum maximum treated with or without molasses, were evaluated to determine fermentative characteristics. The grass was harvested at the boot stage of growth and the material of each treatment was ensiled in separate 1kg mini-silos. Compared to day 0 (control), silage pH dropped significantly at day 7 for molasses-treated silage regardless of initial moisture level. In the untreated silage a slightly lower pH was recorded for the unwilted silage. Molasses treatment resulted in a lower silage pH, higher lactic acid and lower acetic acid concentrations starting from day 7 throughout the fermentation period. Compared to prior wilted silages, lower (p < 0.05) pH, higher lactic acid and lower acetic acid concentrations were recorded for directly cut silages throughout the fermentation period. Molasses had no influence on the nitrogen (N) content of silage, but wilting resulted in a higher N content compared to unwilted silage in presence of molasses. Neither the influence of molasses nor the initial moisture level had a significant effect on ammonia nitrogen (NH3-N) concentration on day 7, but an interaction between molasses addition and moisture level was evident on day 21 and 120. The level of ammonia nitrogen increased with fermentation time. The addition of molasses seemed to be beneficial to the fermentation process and resulted in well preserved silage, whereas the effect of initial moisture condition seems to have little significance.

Photochemical Reaction of VOC Gases on the Visible Light Photocatalyst Surfaces

We report the photochemical reaction of volatile organic compounds (VOC's), such as acetaldehyde and toluene, over nitrogen doped TiO2(TiO-N) under visible light irradiation, using liquid chromatography (LC), gas chromatography (GC) and gas chromatograph mass spectrometer (GC-MS) for gases analysis, and diffuse reflectance fourier transform infrared spectroscopy (DRIFTS) and ion chromatography (IC) for adsorbed organics. We evaluated the photo degradation rates and intermediates for the above gases. As a result, the degradation rates of acetaldehyde gas on TiO-N were 1.2-3 times greater than those on TiO2, and those of toluene gas on TiO-N were 4-49 times greater than those on TiO2. Low concentrations of acetone and acetic acid were produced during the photo degradation of acetaldehyde by the TiO-N. From toluene, very low concentrations of formaldehyde, acetaldehyde, acetone and benzaldehyde gases were produced. We also revealed the decomposition processes of toluene. Results obtained indicate that toluene, weakly adsorbed on the photocatalyst surface, is initially photooxidized to benzaldehyde which adsorbs onto the TiO-N surface more strongly, leading to the formation of ring-opening products such as carboxylic acids and aldehydes. These intermediate products were gradually photodegraded to CO2 and H2O under visible light irradiation.

Influence of pH, water activity and acetic acid concentration on Listeria monocytogenes at 7 °C: Data collection for the development of a growth/no growth model

Growth/no growth models can be used to determine the chance that microorganisms will grow in specific environmental conditions. As a consequence, these models are of interest in the assessment of the safety of foods which can be contaminated with food pathogens. In this paper, growth/no growth data for Listeria monocytogenes (in a monoculture and in a mixed strain culture) are presented. The data were gathered at 7 °C in Nutrient Broth with different combinations of environmental factors pH (5.0–6.0, six levels), water activity (0.960–0.990, six levels) and acetic acid concentration (0–0.8% (w/w), five levels). This combination of environmental factors for the development of a growth/no growth model was based on the characteristics of sauces and mayonnaise based salads. The strains used were chosen from screening experiments in which the pH, water activity and acetic acid resistance of 26 L. monocytogenes strains (LFMFP culture collection) was determined at 30 °C in Brain Heart Infusion broth. The screening showed that most L. monocytogenes strains were not able to grow at a w < 0.930, pH < 4.3 or a total acetic acid concentration > 0.4% (w/w). Among these strains, the ones chosen were the most resistant to one of these factors in the hope that, if the resulting model predicted no growth at certain conditions for those more resistant strains, then these predictions would also be valid for the less resistant strains. A mixed strain culture was also examined to combine the strains that were most resistant to one of the factors. A full factorial design with the selected strains was tested. The experiments were performed in microtiter plates and the growth was followed by optical density measurements at 380 nm. The plates were inoculated with 6 log CFU/ml and twenty replicates were made for each treatment combination. These data were used (1) to determine the growth/no growth boundary and (2) to estimate the influence of the environmental conditions on the time to detection. From the monoculture and mixed strain data, the growth boundary of L. monocytogenes is shown not to be a straight cut-off but a rather narrow transition zone. The experiments also showed that in the studied region, a w did not have a pronounced influence on the position of the growth/no growth boundary while a low concentration of acetic acid (0.2% (w/w)) and a pH decrease from 6.0 to 5.8 was sufficient to significantly reduce the possibility of growth. The determination of the time to detection showed a sifnificant increase at the combinations of environmental conditions near the ‘no growth zone’. For example, at 0.2% (w/w) acetic acid, there was an increase from ± 10 days to 30 days by lowering pH from 5.8 to 5.6 at a w values of 0.985 and 0.979, while at pH 5.4 less than 50% growth occurred for all a w values.

Industrial implementation of black ripe olive storage under acid conditions

Restrictions on the discharge of chloride in wastewater streams have recently increased, and processors of black ripe olives have to look for alternative storage systems to the traditional brines. Ripe olives of the Hojiblanca variety were stored under aerobic and anaerobic conditions in industrial underground tanks for one year. The aerobic systems assayed with or without NaCl produced a continuous consumption of sugars as they diffused from the fruits to the surrounding liquid. At the same time sugars accumulated in the liquid for months when anaerobic conditions were employed and a high concentration of acetic acid was used. In the end, glucose was consumed with time as well and, in addition to yeasts, acetic acid and lactic acid bacteria grew in the cover solutions. The assessment of olives stored under the different systems and processed as black ripe olives revealed that the traditional aerobic brines gave rise to darker and firmer fruits. However, olive industries must eliminate chlorides from their waste streams. Promising new storage systems were (i) anaerobic preservation of olives in water with an initially high concentration of acetic acid, and (ii) aerobic preservation in water with an initially low concentration of acetic acid. Both systems produced a good quality product, free of microbial spoilage and organoleptic defects.

Detoxification procedures of eucalyptus hemicellulose hydrolysate for xylitol production by Candida guilliermondii

Xylitol can be obtained from hemicelullosic fraction of lignocellulosic materials containing d-xylose. A problem associated with the fermentation of hemicellulosic sugars to xylitol is the presence of a broad range of compounds, which inhibit the fermenting microorganisms. These inhibitors can be removed from the hydrolysate by a detoxification method, prior to fermentation. This study describes different detoxification methods of eucalyptus residues hydrolysate to improve xylitol production by Candida guilliermondii. The changes in the concentrations of fermentable sugars and four groups of inhibitory compounds were determined and the fermentability of detoxified hydrolysates was assayed. The applied detoxification methods include: treatment with active charcoal and four different resins (cationic and anionic) in sequence. Ion exchange resins were more efficient than activated charcoal to remove all four major groups of inhibitory compounds without sugar loss. The ion exchange detoxification drastically enhanced the fermentability of the hydrolysate. Under the best assayed operating conditions, 32.7 g/L of xylitol were achieved after 48 h fermentation, which correspond to 0.68 g/L h volumetric productivity and 0.57 g/g xylitol yield factor. In addition, it was verified that low concentrations of acetic acid can have a benefical effect on xylitol productivity.

Method optimization for quantitative analysis of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by liquid chromatography-electrospray ionization mass spectrometry

A simple, sensitive LC-ESI-MS method was optimized for quantitative analysis of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in environmental samples. Under negative ionization mode, HMX can form adduct ions with various organic acids and salts, including acetic acid, formic acid, propionic acid, ammonium nitrate, ammonium chloride, sodium nitrite, and sodium nitrate. Acetic acid was chosen as additive and the ion, [M + CH 3COO] − with m/ z = 355 was used for selective ion monitoring (SIM) in this study. Good sensitivity was achieved with low acetic acid concentration in the mobile phase and relatively low capillary temperature. The method detection limit was 0.78 pg for HMX in standard solution. Linearity ( R 2 > 0.9998) was obtained at low concentrations (0.5–50 μg/L). This method has been used to determine HMX concentrations in water samples and lizard egg samples from an animal exposure study.

In situ probing of insulin aggregation in chromatography effluents with spectroturbidimetry

Probing protein aggregation in situ is quite important for analyzing and developing chromatographic protein purification processes. A spectroturbidimetry method with a photodiode array detector is developed and tested for probing insulin aggregation in solution and determining the aggregation number, n m . All aggregates examined are in the Rayleigh light scattering regime, where the turbidity between 400 and 350 nm is proportional to λ −4 . Insulin at 25 °C in 3.5 N acetic acid is mainly monomeric (non-aggregated). At 25 °C and lower acetic acid concentrations, from 0.1 to 1 N, the average insulin aggregation number n m ranges from 2.9 to 1.6. Aggregates, with n m = 2 – 3 , are found in 2.6 N acetic acid with 20 vol% acetonitrile. In 0.8 N acetic acid with 20 vol% denatured ethanol, n m = 1.2 . At 4 °C, as acetic acid concentration decreases from 3.5 to 0.1 N, n m decreases from 2.4 to 1.8. In 2.8 N acetic acid with 20 vol% denatured ethanol at 4 °C, insulin exists mainly in monomer form. In situ probing of size exclusion chromatography, SEC, effluents in 3.5 N acetic acid at 4 °C shows n m = 1.6 at the fronting portion (a mixture of monomers and dimers or other oligomers) and n m = 1.1 (mostly monomers) at the tailing portion of the main peak. In another example, for LysPro-insulin in reversed phase chromatography at 4 °C, complex elution patterns and broad peaks are due to substantial aggregation. For a linear gradient of acetonitrile from 10 to 60 vol% at 4 °C, n m ranges from 2.2 to 12, in order of elution. For a linear gradient of ethanol from 30 to 50 vol% at 4 °C, n m ranges from 14 to 27, in order of elution. Analytical HPLC results at 25 °C imply that the aggregates are reversible.