Dissociated Form Research Articles

Влияние цетиламина на спектры поглощения и протолитические свойства люмогаллиона и магнезона ХС

The interaction of monoazo compounds lumogallion (LG) and magnezon HS (MHS) with cetylamine (CA) in a wide pH range has been studied using a spectrophotometric method.It has been shown that the formation of ionic associates of CA under the interaction of its cation with sulfo group of azo compounds in the pH range 1–4 does not change the electronic absorption spectra of the azodyes. The interaction of CA at dissociated OH groups conjugated with the π-system of the azo compounds leads to a bathochromic shift in the maximum of the absorption spectrum of the corresponding ionic form of the reagents by 15 and 30 nm for the doubly and triply charged forms of LG, respectively, and by 50 nm for the doubly charged form of MHS. The shift in the maximum of the absorption spectrum is accompanied by the shift in the apparent pK value of the reagents by 2–4 pH units, caused by the binding of the dissociated form of the reagents. The reason for these changes in the absorption spectra and protolytic properties of both reagents is the formation of hydrophobically hydrated ionic associates of azo compounds with the cetylamine cation.

C-Reactive Protein, the Gliovascular Unit, and Alzheimer's Disease.

Alzheimer's disease (AD) pathogenesis is conditioned by the presence of amyloid beta (Aβ) and neuroinflammation. The gliovascular unit (GVU) illustrates the relationship between the vascular components of the brain and glial cells, particularly astrocytes, which are seen as critical elements mainly affected in this disease. In AD patients, the impairment of the GVU is seen as blood-brain barrier breakdown, decreased clearance of Aβ, and chronic inflammatory status. C-reactive protein (CRP) and its monomeric form (mCRP) are associated with endothelial dysfunction and amyloid plaque instability, contributing to neuroinflammation and neurodegeneration. The interconnections between the GVU and the dissociated form of CRP were demonstrated by mCRP implication in vascular permeability that supports inflammation and extravasation of pro-inflammatory cytokines into the brain parenchyma. Astrocytic activation and endfeet function alterations can exacerbate the progression of AD by elevating pro-inflammatory agents and vascular amyloid accumulations. This review aims to emphasize the synergistic link between the GVU and monomers of CRP in the perpetuation of the inflammatory status, exacerbating neurodegeneration and neuroinflammation. Understanding their implication in AD can bring insights into novel therapeutic strategies to reduce AD progression.

Cooperative Protein Dynamics of Heterotetrameric Hemoglobin from Scapharca inaequivalvis.

Hemoglobins achieve cooperative oxygen binding by diverse strategies based on different assemblies of globin subunits. Heterotetrameric hemoglobin from Scapharca inaequivalvis (HbII) consists of two AB-dimers, whose structure closely resembles that of homodimeric hemoglobin from the same organism (HbI). Herein, we investigated the structural dynamics of HbII following carbon monoxide (CO) dissociation using time-resolved resonance Raman (RR) spectroscopy. The observed spectra showed that the heme structure of the transient dissociated form of HbII was similar to that of HbI; however, the transition from the transient dissociated form to the equilibrium unligated form was faster for HbII than for HbI. Furthermore, the dependence of the time-resolved spectra on the yield of CO dissociation revealed that the transition became faster as the number of dissociated ligands increased from one to four. The positive correlation between the rate constants and number of dissociated ligands indicates that the structural transition of HbII following CO dissociation is cooperative.

Membrane-based fermentation enables highly selective caproic acid production from wine lees

Chain elongation is a green chemistry approach to convert organic waste or agro-industrial side-products into caproic acid. Nonetheless, such feedstocks may contain microorganisms and chemical pollutants that could deteriorate the product yield and purity. This study introduces a membrane-based fermentation process designed to isolate the caproic acid producing bacteria from these contaminants. A tubular polysiloxane (silicone) membrane submerged into a fermentor allowed the selective diffusion of ethanol and acetic acid while preventing the cross-over of bacteria and contaminants such as ions. Abiotic tests confirmed that membrane thickness, feedstock pH and flow velocity can be adjusted to independently control the diffusion of ethanol and acetic acid. Thereof, optimal ethanol:acetic acid ratios for chain elongation (6:1) were obtained from a feedstock solution with equimolar (1 M) concentrations of both. In the biotic tests, this resulted in a highly selective (>90 %) caproic acid production at a highest rate of 3.1 g/(L·d). Maintaining the pH above 6.8, thereby keeping most caproic acid in its dissociated form, prevented its back-diffusion through the membrane. Similar caproic acid productivity was achieved from diluted wine lees (1 M ethanol), amended with 1 M acetic acid. In contrast, unamended wine lees resulted in three times lower caproic acid production rate, although the product selectivity remained high (94 %). Downstream processing by acidification and phase separation yielded 6–13 mL/Lfeedstock of an oily product containing up to 784 g/L caproic acid (84.3 % purity). In conclusion, membrane-based fermentation enables highly selective caproic acid production from highly concentrated and unbalanced substrates.

Brain Vascular Expression of Monomeric C-Reactive Protein Is Blocked by C10M Following Intraperitoneal Injection in an ApoE-/- Murine Model of Dyslipidemia: An Immunohistochemical Analysis.

Introduction The neurovascular unit (NVU), comprising vascular and glial cells along with neurons, is vital for maintaining the blood-brain barrier (BBB) and cerebral homeostasis. Dysfunction of the NVU is implicated in key neurodegenerative disorders such as Alzheimer's disease (AD). Monomeric C-reactive protein (mCRP), the dissociated form of native, pentameric C-reactive protein (pCRP), is associated with enhanced pro-inflammatory responses in the vascular system, leading to increased permeability and potential NVU disruption. Methods This study utilized ApoE-/- mice receiving a high-fat diet which were injected intraperitoneally with either mCRP or mCRP together with a small molecule inhibitor (C10M) and investigated the deposition of mCRP and CD105 expression in the brain parenchyma and its localization within the microvasculature. Results Histological analysis revealed significant mCRP deposition in brain microvessels and neurons, indicating potential disruption of the BBB and neuronal damage. Moreover, co-administration of C10M effectively blocked mCRP accumulation in the brain parenchyma, suggesting its potential as a therapeutic agent for effectively inhibiting inflammation-associated degenerative changes. Immunohistochemical staining demonstrated co-localization of mCRP with CD105, indicating potential angiogenic activation and increased susceptibility to inflammatory insult. Discussion These findings provide evidence supporting the potential role of mCRP as a contributor to neuroinflammation in individuals with chronic systemic inflammation. Conclusion Further studies in human subjects should help validate the efficacy of C10M in preventing or halting neurodegeneration in conditions such as AD and stroke-associated dementia.

Photocatalytic reforming of ethanol to produce hydrogen: Effect of anatase doped with NiO on products and reaction pathways

Photocatalytic hydrogen production is of great significance for the transformation of energy system. To improve the hydrogen production performance, nano-photocatalysts including pure TiO2 and NiO-TiO2 were prepared by sol-gel method in this paper. To unravel reaction intermediates and pathways, the adsorption experiments and photocatalytic reaction of ethanol over the photocatalysts were carried out in combination with in situ DRIFTS technique, and the main products in the photocatalytic process were detected through gas chromatography. The results showed that 2NiO-TiO2 as the optimum photocatalyst can yield the maximum H2 rate at 20.10 mmol g−1 h−1. For the adsorption of ethanol on TiO2 and 2NiO-TiO2, the molecular form of ethanol is more dominant than the dissociated form, and CH3CH2OTi is more easily generated on 2NiO-TiO2 than pure TiO2. The hydrogen production pathway changes by doping with NiO, reducing the production of acetic acid and aldehydes and producing the important intermediate CH2CHOTi.

Arsenic Contents, Speciation and Toxicity in Germinated Rice Alleviated by Selenium.

Rice can accumulate more organic and inorganic arsenic (iAs) than other crop plants. In this study, the localization of As in rice grains was investigated using High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS) based on 26 rice varieties collected from two provinces. In all the samples, the total As contents in polished rice were 0.03-0.37 mg/kg, with average values of 0.28 and 0.21 mg/kg for two sample sets. The results of the determination of arsenic speciation in different components of rice grain showed that in the polished and brown rice the mean value of arsenite (As(III)) was nearly twice than that of arsenate (As(V)). The regional difference was observed in both total As contents and As speciation. The reason may be that As(III) is more mobile than As(V) in a dissociated form and because of soil properties, rice varieties, and the growing environment. The proportion of iAs and the total As in rice bran was higher than that in polished rice, and this is because As tends accumulate between the husk and the endosperm. In our study, selenium could alleviate the risk of arsenic toxicity at the primary stage of rice growth. Co-exposure to As and Se in germinated rice indicated that the reduction in As accumulation in polished rice reached 73.8%, 76.8%, and 78.3% for total As, As(III), and As(V) when compared with rice treated with As alone. The addition of Se (0.3 mg/kg) along with As significantly reduced the As amount in different parts of germinated rice. Our results indicated that Se biofortification could alleviate the As accumulation and toxicity in rice crops.

Evaluation of Oxalate Content in Cassava Roots and Sweet Potato Tubers in Areka, Ethiopia

Oxalic acid (or its dissociated form oxalate) is a product of protein metabolism and is one of the important nutrients in the human diet. Regular consumption of large amounts of food with high oxalate contents over a long period may result in nutrient deficiencies notably calcium and contribute to kidney stone formation. The aim of this study is to assess some physicochemical properties and the oxalate content of cassava and sweet potato grown in Areka, Ethiopia using titration and UV-visible spectrophotometric methods. The moisture content of dry flour and fresh roots of cassava was found to be 10.33 and 55.27 %, respectively, while the moisture content of dry flour and fresh tuber of sweet potato was 9.07 and 68.47 %, respectively. The ash content of the flour sample of cassava and sweet potato was 3.60 and 4.13 %, respectively. The pH of the flour sample of cassava and sweet potato was 6.23 and 6.13, respectively. All physicochemical parameters were significantly different (P < 0.05). The oxalate content determination was done using titration and UV-visible spectrophotometer methods. The oxalate level of samples using the titration method gave 77.66 and 197.90 mg/100g for cassava and sweet potato, respectively. By the UV-visible spectrophotometer, the oxalate content of cassava was 151.19 and 153.56 mg/100g for sweet potato. The results of the statistical analysis on the generated data indicated that there was a significant difference at p≤ 0.05 among the physicochemical investigated in this study. Keywords: Cassava, oxalate, physicochemical, sweet potato, UV-visible spectrophotometer. DOI: 10.7176/FSQM/117-02 Publication date: July 31 st 2022

Adsorption and Mechanism of Glycine on the Anatase with Exposed (001) and (101) Facets

As a widely existing mineral types on Earth, semiconductor minerals play an important role in the origin of life and the material geochemical cycle. The first step of peptide formation is amino acid adsorption on the mineral surface, but the role and mechanism of different crystal facets of semiconductor minerals are not well understood. Anatase (TiO2) with exposed (001) facets was synthesized by a hydrothermal method, and then analyzed and compared with the purchased ordinary anatase (TiO2) for the adsorption of glycine, the simplest amino acid. XRD, SEM and TEM results show that the hydrothermally synthesized anatase (TiO2) has a good anatase crystal form, which is micro-nano-scale flake particles and mainly composed of (001) facets. The results of HPLC used in the adsorption experiment showed that under optimal conditions (pH 5 to 6, an adsorption time of 24 h, and an initial concentration of 0.09 mol/L), the adsorption quantity of glycine on anatase (TiO2) with exposed (001) facets may reach 10 mg/m2, which is larger than that for ordinary anatase (TiO2) with exposed (101) facets. Based on a combination of various characterizations and simulation calculations, the results proved that anatase can activate thermodynamically stable γ-glycine to β-glycine. The adsorption of glycine on anatase (TiO2) has two forms, one is the zwitterionic form in which the carboxyl group forms a bridge structure with two Ti atoms connected by surface bridging oxygen, and the dissociated form is in which the amino group forms a bond with the surface Ti atom. Among these, glycine is mainly adsorbed to anatase by dissociative molecules on the anatase (TiO2) with exposed (001) facets and by zwitterion adsorption on the anatase (TiO2) with exposed (101) facets. This research elucidates the conditions and mechanism of amino acid adsorption by semiconductor minerals in weak acidic environment, which is similar to the environmental pH that was beneficial to the formation of life on the early Earth. Therefore, these can provide a reference for the further study of the role of semiconductor minerals in the adsorption and polymerization of small biomolecules in the origin of life.

Effect of acid treated HY zeolites in adsorption of mesosulfuron-methyl.

Pollution of surface water and groundwater by bulky molecules such as pesticides has been recognized as a major problem in many countries due to their persistence in aquatic environment and potential adverse health effects. The main purpose of this study is the development of a capable adsorbent to remove these bulky molecules from wastewater such as the pesticide Mesosulfuron-Methyl (MM) by reducing the diffusion path, to overcome the problems of diffusional limitations on microporous adsorbents. The adsorption of mesosulfuron-methyl (MM) from aqueous solution is curried out using treated acid HY zeolite. Batch sorption equilibrium and kinetic experiments are conducted to evaluate the efficiency of these materials. Parent zeolites and their derivatives have been characterized by nitrogen adsorption-desorption, pyridine chemisorption followed by infrared spectroscopy and X-ray fluorescence. The acid treatment leads to an increase in the specific surface from 691 to 853 m2 g- 1 for HY(30) and from 631 to 806 m2 g- 1 for the HY(16.6) zeolites. It also leads to a reduction in Lewis acidity from 74 to 25 µmol g- 1 and from 135 to 31 µmol g- 1 for HY(30) and HY(16.6) zeolites respectively, and increases the adsorbent-adsorbate interaction. The adsorption capacity increased from 83 to 99 % after acid treatment. The equilibrium adsorption time is decreased from 15h to 10min for the HY(30)_A and from 20h to 20min for the HY(16.6)_A for an initial concentration of 20mg L- 1. The adsorption capacity depends on the pH solution, and the neutral form of the MM is more easily adsorbed into zeolite than the dissociated form via the framework bridged oxygen atoms. For all the samples, the pseudo-second-order kinetic model fits very well with the experimental data. In the case of the modified zeolites, the approaching equilibrium factor R w decreases from 0.08183 to 0.00008 when the Lewis acid sites decrease; indicating that the equilibrium is reached more quickly. S-shape adsorption isotherms indicates that cooperative adsorption phenomena. Nevertheless, the shape of acid treated zeolites evolves to an L type indicating a significant enhancement of the adsorbent - adsorbate interactions inducing better adsorption efficiency. Mesosulfuron-methyl adsorption has been successfully enhanced after acid treatments of zeolites HY.

Lactate Like Fluconazole Reduces Ergosterol Content in the Plasma Membrane and Synergistically Kills Candida albicans.

Candida albicans is an opportunistic pathogen that induces vulvovaginal candidiasis (VVC), among other diseases. In the vaginal environment, the source of carbon for C. albicans can be either lactic acid or its dissociated form, lactate. It has been shown that lactate, similar to the popular antifungal drug fluconazole (FLC), reduces the expression of the ERG11 gene and hence the amount of ergosterol in the plasma membrane. The Cdr1 transporter that effluxes xenobiotics from C. albicans cells, including FLC, is delocalized from the plasma membrane to a vacuole under the influence of lactate. Despite the overexpression of the CDR1 gene and the increased activity of Cdr1p, C. albicans is fourfold more sensitive to FLC in the presence of lactate than when glucose is the source of carbon. We propose synergistic effects of lactate and FLC in that they block Cdr1 activity by delocalization due to changes in the ergosterol content of the plasma membrane.

Insight into the roles of ammonia during direct alcohol amination over supported Ru catalysts

The direct amination of alcohols with ammonia is a promising route to make primary amines, but a full understanding of various parameters, especially the effect of co-adsorbed nitrogen-containing species on the catalyst surface during amination, has still been lacking. Here, we report that the presence of dissociated ammonia species on Ru nanoparticles substantially enhances its activity in catalyzing the dehydrogenation step that is kinetically-relevant to amination. Kinetic, spectroscopic, and theoretical methods are combined to highlight how ammonia affects this rate-determining step: in the dissociated form the surface NHx species interact with the alcohol reactant and lower the corresponding barrier of OH scission, thus promoting the activity on Ru. In contrast to Pd-based catalysts, the N atom in the generated R-NH2 product binds moderately strongly with Ru sites, thus inhibiting the formation of undesired secondary amine via further CN coupling. This work unveils the overlooked role of ammonia in the amination reaction over Ru-based catalysts.

Effect of pH and temperature on the aggregation behaviour of dirhamnolipid biosurfactant. An experimental and molecular dynamics study

HypothesisPseudomonas aeruginosa dirhamnolipid (diRL) has been shown to form aggregates of different size and structure, under various conditions. Due to the presence of a carboxyl group in the molecule, it is expected that pH would strongly affect this aggregation behaviour. In addition, preliminary observations of temperature-induced changes in the states of aggregation of diRL supported the need of further investigation. ExperimentsA systematic experimental study, using differential scanning calorimetry (DSC), small-angle Xray diffraction (SAXD), and Fourier-transform infrared spectroscopy (FTIR), has been carried out to characterize pH and temperature driven changes in the aggregation behavior of diRL biosurfactant. Molecular dynamics (MD) simulations, supported by the experimental results, allowed depicting molecular details on formation of diRL membranes and other aggregated structures under various physicochemical conditions. FindingsDiRL could adopt fairly organized multilayered structures (membranes) at low pH and temperature, which became highly disordered upon increasing either of these parameters. The effect of pH on the gauche/all-trans conformer ratio of the diRL acyl chains was not of significance, whereas temperature-induced effects were observed. For the first time it is described that diRL underwent an endothermic thermotropic transition with Tc = 34 °C as observed by DSC, at pH 4.5 (protonated diRL), but not at pH 7.4 (unprotonated diRL). FTIR confirmed these findings, showing a significant additional disordering of the all-trans acyl chains upon increasing temperature around that same value in the protonated form, an effect not observed for the dissociated form of the biosurfactant. In addition, at pH 7.4, changing temperature did not modify the hydration state of the polar moiety of diRL, whereas at pH 4.5 a significant decrease in the hydration state around 34 °C took place. SAXD data showed that protonated diRL formed multilayered structures at 20 °C, which converted into poorly correlated layers at 50 °C. MD simulations supported these findings, showing that the membrane-like structures formed by protonated diRL at 20 °C became unstable at higher temperatures, tending to form other structures, which could be micelles or other type of layered structures, whereas the negatively charged form of diRL organized in micelle-type aggregates in the whole range of temperature under study.

The day the clock stopped. Primitive states of unintegration, multidimensional working through and the birth of the analytical subject.

This paper is based on one idea and built around one clinical experience that helped me to broaden my comprehension of it. The idea, underlying the work of several authors, is that when the analytic field is saturated with primitive and unintegrated mental contents, the analyst's somatic countertransference is a precious indicator of a deep, dissociated form of communication. The clinical experience concerns the difficult elaboration of a complex, multifaceted countertransference that took place during the early stages of the analysis of a sensitive patient who used to communicate in a very dissociated way and that I found hard to contain. This experience, closely described in the article, led me to formulate the clinical idea that the transference field may be made of distinct layers (psychoid, affective, verbal), and that each one of them may potentially convey dissociated, even contrasting bits of information. The corollary of this is that the analyst should be ready to accept contrasting sensations, feelings and thoughts at the same time, as they might be the basic ingredients of a complex reverie. The analyst could find himself/herself in front of his/her own internal unelaborated multiplicity before a symbolic image may emerge to link the scattered pieces of the experience. Nevertheless, the heart of this paper is not about suggesting an idea, but in the sharing of a complex working through, which fostered the birth of a new, more human relational perspective: the capacity of being together in time, in a transitional space where there is neither total separation nor fusion.

Morphological features of the placenta in obese women

Hypothesis/Aims of study. Obesity and severe chronic somatic pathology in a woman leads to a rapid depletion of compensatory and adaptive reserves of the placenta and to the progression of circulatory and dystrophic changes, which causes intrauterine growth retardation and reduces the likelihood of a favorable course of pregnancy and childbirth. The aim of this study was to assess the morphological features of the vascular component of placental villi in obese women.
 Study design, materials and methods. Histological and immunohistochemical studies were conducted on 41 placentas from obese patients with and without gestational diabetes mellitus and from healthy patients, endothelial marker CD34+ expression being assessed in chorionic villi.
 Results. In obese patients, chronic placental insufficiency is presented in most cases as a dissociated form with persistence of not only mature but also immature villi, which indicates early structural pathology of the placenta.
 Conclusion. Obesity in women contributes to more frequent chronic placental insufficiency with severe circulatory disorders and varying degrees of severity of compensatory and adaptive changes.

Monomeric C-Reactive Protein - A Feature of Inflammatory Disease Associated With Cardiovascular Pathophysiological Complications?

Monomeric C-reactive protein (mCRP), the dissociated form of native C-reactive protein, is a critical molecule that causes and perpetuates inflammation in serious diseases. It has 'adhesive'-like properties causing aggregation of blood cells and platelets, and can stick permanently within arterial tissue where it can contribute to further complications including thrombosis, linking it potentially to atherosclerosis and subsequent acute coronary events. In this mini review, we discuss briefly the implications and the potential value of measuring and manipulating it for clinical diagnostics and therapeutic purposes.

An Evaluation of Oxalate Content in Cassava Roots and Sweet Potato Tubers in Areka, Ethiopia

Oxalic acid (or its dissociated form oxalate) is a result of protein metabolism and is among the important nutrients in the human diet. Regular consumption of large amounts of food with high oxalate contents over a long period may result in nutrient deficiencies notably calcium and contribute to kidney stone formation. The aim of current research is to determine some physicochemical characteristics as well as the oxalate content of cassava in addition to sweet potato grown in Areka, Ethiopia using titration and UV-visible spectrophotometric methods. The moisture content of dry flour and fresh roots of cassava was found to be 10.33 and 55.27 %, respectively, while the moisture content of dry flour and fresh tuber of sweet potato was 9.07 and 68.47 %, respectively. The ash content of the flour sample of cassava and sweet potato was 3.60 and 4.13 %, respectively. The pH of the flour sample of cassava and sweet potato was 6.23 and 6.13, respectively. Oxalate content determination was done using titration and UV-visible spectrophotometer methods. The oxalate level of samples using the titration method gave 77.66 and 197.90 mg/100g for cassava and sweet potato, respectively. By the UV-visible spectrophotometer, the oxalate content was 151.19 and 153.56 mg/100g for cassava and sweet potato, respectively. Statistical analysis on the generated data indicated that all physicochemical investigated in this study have significance difference at p≤ 0.05.

Biostimulant Potential of Acetic Acid Under Drought Stress Is Confounded by pH-Dependent Root Growth Inhibition.

Recent reports of acetic acid-induced drought tolerance and avoidance across a diverse range of plant species encourage consideration of this low-cost commodity organic acid as a biostimulant. These results are surprising as they contrast with earlier studies showing pH-dependent root growth inhibition at similar concentrations. We test the hypothesis that the concentration of the membrane permeable undissociated form of acetic acid (CH3COOH) selectively inhibits maize root growth, and subsequently evaluate its impact on seedling water use and growth under deficit irrigation. We demonstrate conclusively for the first time that when germinating maize on filter paper, low pH exacerbates, and high pH mitigates, this inhibition of root growth in a predictable manner based on the dissociation constant of acetic acid. The buffering capacity of potting media can reduce this root damage through keeping the acetic acid primarily in the membrane impermeable dissociated form (CH3COO–) at near neutral pH, but peat substrates appear to offer some protection, even at low pH. While both deficit irrigation and acetic acid reduced water use and growth of maize seedlings outdoors, there was no significant interaction between the treatments. Twenty nine millimolar total acetic acid (CH3COOH + CH3COO–) reduced transpiration, compared to lower and higher concentrations, but this did not specifically improve performance under reduced water availability, with parallel declines in shoot biomass leading to relatively consistent water use efficiency. Any acetic acid biostimulant claims under water stress should characterize its dissociation level, and exclude root damage as a primary cause.

Spontaneously Blinking Fluorophores Based on Nucleophilic Addition/Dissociation of Intracellular Glutathione for Live-Cell Super-resolution Imaging.

Single-molecule localization microscopy (SMLM) allows the reconstruction of super-resolution images but generally requires prior intense laser irradiation and in some cases additives to induce blinking of conventional fluorophores. We previously introduced a spontaneously blinking rhodamine fluorophore based on an intramolecular spirocyclization reaction for live-cell SMLM under physiological conditions. Here, we report a novel principle of spontaneous blinking in living cells, which utilizes reversible ground-state nucleophilic attack of intracellular glutathione (GSH) upon a xanthene fluorophore. Structural optimization afforded two pyronine fluorophores with different colors, both of which exhibit equilibrium (between the fluorescent dissociated form and the nonfluorescent GSH adduct form) and blinking kinetics that enable SMLM of microtubules or mitochondria in living cells. Furthermore, by using spontaneously blinking fluorophores working in the near-infrared (NIR) and green ranges, we succeeded in dual-color live-cell SMLM without the need for optimization of the imaging medium.

Engineering Oleaginous Yeast as the Host for Fermentative Succinic Acid Production From Glucose.

Oleaginous yeast Yarrowia lipolytica is a prospective host for production of succinic acid. The interruption of tricarboxylic acid cycle through succinate dehydrogenase gene (SDH) deletion was reported to result in strains incapable of glucose utilization and this ability had to be restored by chemical mutation or long adaptive laboratory evolution. In this study, a succinate producing strain of Y. lipolytica was engineered by truncating the promoter of SDH1 gene, which resulted in 77% reduction in SDH activity but did not impair the ability of the strain to grow on glucose. The flux toward succinic acid was further improved by overexpressing the genes in the glyoxylate pathway and the oxidative TCA branch, and expressing phosphoenolpyruvate carboxykinase from Actinobacillus succinogenes. A short adaptation on glucose reduced the lag phase of the strain and increased its tolerance to high glucose concentrations. The resulting strain produced 7.8 ± 0.0 g/L succinic acid with a yield of 0.105 g/g glucose in shake flasks without pH control, while mannitol (11.8 ± 0.8 g/L) was the main by-product. Further investigations showed that mannitol accumulation was caused by low pH stress and buffering the fermentation medium eliminated mannitol formation. In a fed-batch bioreactor in mineral medium at pH 5, at which point according to Ka values of succinic acid, the major fraction of product was in acidic form rather than dissociated form, the strain produced 35.3 ± 1.5 g/L succinic acid with 0.26 ± 0.00 g/g glucose yield.