Nonionized Form Research Articles

Influence of boric acid on the speciation of iron (III) in aqueous solutions

During the work, the speciation of iron (III) was studied at the concentration of ~ 1∙10–5 mol/dm3 in aqueous solutions in the presence of boric acid at a concentration of 5–20 g/dm3 in a wide pH range using ion exchange, ultrafiltration and centrifugation methods. The regions of existence of ionic and nonionic forms of iron (III) were determined by ion exchange in solutions with different boric acid concentrations. Experimental data have shown that the pH of the onset of iron (III) colloid formation shifts in the presence of boric acid. The formation of complex compounds of iron (III) with polyborate ions in the neutral – slightly alkaline pH region was established by ultrafiltration and centrifugation. As shown in the paper, the increase in the concentration of boric acid in solution leads to the increase in the region of existence of the supposed complexes. The identified features of the behavior of iron (III) in solutions containing boric acid determine the possibility of using ion exchange and membrane separation methods for purifying solutions. Information about the physical-chemical properties of various metal-ions can provide optimal conditions for the purification of liquid radioactive waste at various nuclear industry facilities.

Atypical enantioseparation of a non-ionic form of allantoin with Cinchona alkaloid-based zwitterionic chiral stationary phases

Allantoin represents a compound widely employed in pharmaceutical and cosmetic fields. Its safety has been acknowledged by regulatory bodies such as the US Food and Drug Administration, the European Commission for Cosmetics and Consumer and Health and European Directorate for the Quality of Medicines & HealthCare. This justifies its wide use in dermatological/cosmetic formulations and allows their safe use.Allantoin possesses an asymmetric carbon atom, resulting in two enantiomers, with the (S)-enantiomer predominating in plants, although racemization may potentially occur during manufacturing processes. Notably, literature currently lacks enantioselective LC methods for allantoin analysis.In this study, two zwitterionic Cinchona alkaloid-based chiral stationary phases (CSPs), commercially known as CHIRALPAK® ZWIX(+) (CSP1) and CHIRALPAK® ZWIX(-) (CSP2), were utilized for the enantioseparation of allantoin under polar-ionic conditions. By employing a mobile phase consisting of acetonitrile/methanol/water/acetic acid (96:2:2:0.1, v/v/v/v), nearly complete baseline separation (with α=1.08) of allantoin enantiomers was achieved in less than 15 min with both CSPs. Due to the “pseudo-enantiomeric” nature of the two chiral selectors (quinine-based in CSP1 and quinidine-based in CSP2), an inversion of the enantiomer elution order was observed with the two CSPs under identical experimental conditions. Remarkably, this represents a rare instance where these CSPs demonstrate the ability to enantioseparate a non-ionic, non-ionizable species.The application of a molecular dynamics in silico protocol proved useful in elucidating the retention mechanism in depth, casting light on the central role of the H-bond formation and the involvement of the anionic moiety of the CSP 1.

Water-soluble dye – ZnII octacarboxy substituted tetrapyrazinoporphyrazine: Spectral-luminescence study of behavior in aqueous solutions

ZnII complex of octacarboxy substituted tetrapyrazinoporohyrazine, ZnTPyzPA(COOH)8, was prepared by mild alkaline hydrolysis of the corresponding octaethyl ester, ZnTPyzPA(COOEt)8, which was synthesized by template cycloteramerization of 5,6-di(ethoxycarbonyl)pyrazine-2,3-dicarbonitrile in the presence zinc(II) acetate in o-dichlorobenzene. Both complexes were characterized by IR, UV–vis, NMR spectroscopy (1H, 13C). Conformational analysis performed by DFT method in agreement with spectral study indicates that one of COOH group in each pyrazine ring participates in intramolecular hydrogen bonding with the adjacent pyrazine nitrogen atom. Unlike octacarboxy substituted ZnII phthalocyanine, ZnTPyzPA(COOH)8 remains non-aggregated not only in the octaanionic form present in the basic medium but also in tetraanioinic form existing in acid aqueous solutions since intramolecular H-bonding prevents intermolecular interactions. However, the fluorescence is almost completely quenched for tetraanion which can be related to the proton transfer in the excited state from carboxylic group to the pyrazine nitrogen. Aggregation is observed only for non-ionized form of ZnTPyzPA(COOH)8 existing in strongly acidic medium (1 M HCl solution, pH < 1).

Unraveling energy transfer and fluorescence quenching dynamics in biomolecular complexes: a comprehensive study of imiquimod-rifampicin interaction.

In nature, numerous biomolecules are implicated in charge transfer (CT) and energy transfer (ET) mechanisms crucial for fundamental processes such as photosynthesis. Unveiling these mechanisms is pertinent to multiple disciplines including chemistry, engineering and biochemistry. This article presents a detailed study involving two molecules forming a model system with efficient ET properties. Specifically, their complex exhibits dark quenching phenomena arising from fluorescence resonance energy transfer (FRET) from the donor (imiquimod) to the acceptor (rifampicin). In addition, the energy transfer properties were also elucidated by considering the two forms of rifampicin (RIF), non-ionic and zwitter-ionic in the solution. Supplemented by spectroscopic findings, molecular dynamics simulations and time dependent density functional theory (TD-DFT) calculations conclusively validate the ET properties from imiquimod (IMQ) to RIF forms. Interestingly, these ET processes were found to be associated with pi-pi and hydrogen bond interactions. Their contribution was observed to depend upon the non-ionic and zwitter-ionic form of RIF.

Malachite green-derivatized cationic comb-type copolymer acts as a photoresponsive artificial chaperone

Molecular chaperones play vital roles in various physiological reactions by regulating the folding and assembly of biomacromolecules. We have demonstrated that cationic comb-type copolymers exhibit chaperone activity for anionic biomolecules including DNA and ionic peptide via the formation of soluble interpolyelectrolyte complexes. The development of smart artificial chaperones that can be spatiotemporally controlled by a remotely guided signal would expand the functions of artificial chaperones. Herein, to enable photocontrol of chaperone activity, a cationic comb-type copolymer bearing malachite green as a photoresponsive unit was designed. We first prepared a series of carboxylic acid derivatives of malachite green identified a derivative that could be quickly and quantitatively converted to the cationic form from the nonionic form by photoirradiation. This derivative was conjugated to the cationic comb-type copolymer, poly(allylamine)-graft-poly(ethylene glycol) through a condensation reaction. Upon photoirradiation, the copolymer bearing 9 mol% malachite green enhanced the membrane disruptive activity of acidic peptide E5 and induced morphological changes in liposomes. This demonstration of photoresponsive activation of chaperoning activity of a copolymer suggests that the installation of carboxyl derivatives of malachite green will impart photoresponsiveness to various materials including biopolymers.

Towards green flotation: Investigating the effect of rhamnolipid biosurfactant on single bubble adhesion dynamics

In this study we performed an experimental analysis of the influence of rhamnolipid (RL) biosurfactant produced by Pseudomonas aeruginosa on the dynamics of bubble adhesion onto model surfaces of various hydrophobicity. The attachment time of a single bubble to a solid surface with contact angles of 6, 34, 49 and 80° was evaluated at different concentrations of RL in the range of 0 to 500 mg·dm−3, both at pH 5 (non-ionic form) and pH 10 (anionic form). The dependence of the three-phase contact (TPC) formation time on biosurfactant concentration was determined by monitoring the bubble-solid surface interactions using a high-speed camera. It was found that as the concentration of RL rises, the formation time of the TPC extends as a result of an increase in the film drainage time. A significant effect of RL on the process of TPC expansion (lower rate) and the size of the contact area between the bubble and the surface (smaller surface area) was also noted. This study provides a better understanding of the effect of one of the most popular biosurfactants on the fundamental act of the flotation process: attachment of the particle to the bubble.

Templated Reactive Crystallization of Active Pharmaceutical Ingredient in Hydrogel Microparticles Enabling Robust Drug Product Processing

Commercialization of most promising active pharmaceutical ingredients (APIs) is impeded either by poor bioavailability or challenging physical properties leading to costly manufacture. Bioavailability of ionizable hydrophobic APIs can be enhanced by its conversion to salt form. While salt form of the API presents higher solution concentration than the non-ionized form, poor physical properties resulting from particle anisotropy or non-ideal morphology (needles) and particle size distribution not meeting dissolution rate targets can still inhibit its commercial translation. In this regard, API physical properties can be improved through addition of non-active components (excipients or carriers) during API manufacture. In this work, a facile method to perform reactive crystallization of an API salt in presence of the microporous environment of a hydrogel microparticle is presented. Specifically, the reaction between acidic antiretroviral API, raltegravir and base potassium hydroxide is performed in the presence of polyethylene glycol diacrylamide hydrogel microparticles. In this bottom-up approach, the spherical template hydrogel microparticles for the reaction lead to monodisperse composites loaded with inherently micronized raltegravir-potassium crystals, thus improving API physical properties without hampering bioavailability. Overall, this technique provides a novel approach to reactive crystallization while maintaining the API polymorph and crystallinity.

Solvolysis of 2’-deoxyribonucleosides and oligo-2’-deoxyribonucleotides in aqueous pyrrolidine or ammonia solutions

To assess the feasibility of high-temperature aminolysis of deoxyribooligonucleotides containing rare bases as a method to determine their base sequence, the 2’-β-D-deoxyribosides of 5-bromouracil, 2-aminopurine, uracil, adenine, cytosine, 5-methylcytosine, hypoxanthine, N6-methyladenine, N4-ethylcytosine, and guanine were compared as to their rate of degradation in 0.5 M aqueous pyrrolidine at 110 °C, conditions used earlier in the analysis of oligonucleotides containing only the canonical bases. The reaction mixtures were analyzed by chromatography on Zorbax XDB-CN and UV absorption spectroscopy. The first-order rate constants for the nucleoside degradations decreased in the above order, spanning a wide range of reactivities. Some of these nucleosides were also tested in 0.5 M aqueous ammonia at 110 °C, giving similar first-order rate constants, except for 2’-deoxyguanosine, which is much more reactive with ammonia, due to the lower basicity of this reagent, leaving a larger proportion of the nucleoside in the non-ionized form, susceptible to nucleophilic attack at the base. Short oligothymidylates containing a single 2-aminopurine, adenine, guanine, or cytosine unit in central position were tested in pyrrolidinolysis, to determine the cleavage rates at these sites and the dependence of these cleavage rates on oligonucleotide length. A model decadeoxyribonucleotide containing all four canonical bases was also pyrrolidinolyzed, followed by ion-exchange chromatography, to deduce the nucleotide sequence from the resulting chromatographic profile.

Quantum Mechanical Prediction of Dissociation Constants for Thiazol-2-imine Derivatives.

As weak acids or bases, in solution, drug molecules are in either their ionized or nonionized states. A high degree of ionization is essential for good water solubility of a drug molecule and is required for drug-receptor interactions, whereas the nonionized form improves a drug's lipophilicity, allowing the ligand to cross the cell membrane. The penetration of a drug ligand through cell membranes is mainly governed by the pKa of the drug molecule and the membrane environment. In this study, with the aim of predicting the acetonitrile pKa's (pKa(MeCN)) of eight drug-like thiazol-2-imine derivatives, we propose a very accurate and computationally affordable protocol by using several quantum mechanical approaches. Benchmark studies were conducted on a set of training molecules, which were selected from the literature with known pKa(water) and pKa(MeCN). Highly well-correlated pKa values were obtained when the calculations were performed with the isodesmic method at the M062X/6-31G** level of theory in conjunction with SMD solvation model for nitrogen-containing heterocycles. Finally, experimentally unknown pKa(MeCN) values of eight thiazol-2-imine structures, which were previously synthesized by some of us, are proposed.

Integrated CO2 capture and electrochemical upgradation: the underpinning mechanism and techno-chemical analysis.

Coupling post-combustion CO2 capture with electrochemical utilization (CCU) is a quantum leap in renewable energy science since it eliminates the cost and energy involved in the transport and storage of CO2. However, the major challenges involved in industrial scale implementation are selecting an appropriate solvent/electrolyte for CO2 capture, modeling an appropriate infrastructure by coupling an electrolyser with a CO2 point source and a separator to isolate CO2 reduction reaction (CO2RR) products, and finally selection of an appropriate electrocatalyst. In this review, we highlight the major difficulties with detailed mechanistic interpretation in each step, to find out the underpinning mechanism involved in the integration of electrochemical CCU to achieve higher-value products. In the past decades, most of the studies dealt with individual parts of the integration process, i.e., either selecting a solvent for CO2 capture, designing an electrocatalyst, or choosing an ideal electrolyte. In this context, it is important to note that solvents such as monoethanolamine, bicarbonate, and ionic liquids are often used as electrolytes in CO2 capture media. Therefore, it is essential to fabricate a cost-effective electrolyser that should function as a reversible binder with CO2 and an electron pool capable of recovering the solvent to electrolyte reversibly. For example, reversible ionic liquids, which are non-ionic in their normal forms, but produce ionic forms after CO2 capture, can be further reverted back to their original non-ionic forms after CO2 release with almost 100% efficiency through the chemical or thermal modulations. This review also sheds light on a focused techno-economic evolution for converting the electrochemically integrated CCU process from a pilot-scale project to industrial-scale implementation. In brief, this review article will summarize a state-of-the-art argumentation of challenges and outcomes over the different segments involved in electrochemically integrated CCU to stimulate urgent progress in the field.

Volatilization Potential of Per- and Poly-fluoroalkyl Substances from Airfield Pavements and during Recycling of Asphalt.

Per‐ and poly‐fluoroalkyl substances (PFAS) in water are typically present in their ionic (nonvolatile) forms; however, these can transition to their nonionic (volatile) forms when in contact with organic solvents and organic matrices. In particular, when PFAS are dissolved in organic solvents such as residues left from firefighting foams, fuels, and bitumen present in asphalt, the equilibrium between ionic and nonionic forms can trend toward more volatile nonionic forms of PFAS. We assessed the volatility of common PFAS based on calculated and available experimental data across ambient temperature ranges experienced by airfield pavements and at elevated temperatures associated with reworking asphalts for reuse. Volatilities are shown to be comparable to hydrocarbons in the semivolatile range, suggesting that volatilization is a viable loss mechanism for some PFAS that are nonvolatile in water. The present study points to future investigative needs for this unexplored mass loss mechanism and potential exposure pathway. Environ Toxicol Chem 2022;41:2202–2208. © 2022 Commonwealth of Australia. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Bacterial Membranes Are More Perturbed by the Asymmetric Versus Symmetric Loading of Amphiphilic Molecules.

Characterizing the biophysical properties of bacterial membranes is critical for understanding the protective nature of the microbial envelope, interaction of biological membranes with exogenous materials, and designing new antibacterial agents. Presented here are molecular dynamics simulations for two cationic quaternary ammonium compounds, and the anionic and nonionic form of a fatty acid molecule interacting with a Staphylococcus aureus bacterial inner membrane. The effect of the tested materials on the properties of the model membranes are evaluated with respect to various structural properties such as the lateral pressure profile, lipid tail order parameter, and the bilayer’s electrostatic potential. Conducting asymmetric loading of molecules in only one leaflet, it was observed that anionic and cationic amphiphiles have a large impact on the Staphylococcus aureus membrane’s electrostatic potential and lateral pressure profile as compared to a symmetric distribution. Nonintuitively, we find that the cationic and anionic molecules induce a similar change in the electrostatic potential, which points to the complexity of membrane interfaces, and how asymmetry can induce biophysical consequences. Finally, we link changes in membrane structure to the rate of electroporation for the membranes, and again find a crucial impact of introducing asymmetry to the system. Understanding these physical mechanisms provides critical insights and viable pathways for the rational design of membrane-active molecules, where controlling the localization is key.

THE AVAILABILITY STATUS OF BORON IN THE CULTIVATED SOIL OF NEPAL

Boron is available in nature in rocks and deposits and the availability is influenced by soil organic matter, soil pH, soil texture, and temperature and is taken up by plants in non-ionic form H3BO3 (boric acid) but this concentration account for only about 10% of total soil boron leading to boron deficiency. Also, boron toxicity may occur in low rainfall, extremely alkaline, and saline soils harming plants’ growth and development. Boron shortage and toxicity in plants have a fairly narrow range, and both are detrimental. Hence, it is needed to critically balance boron homeostasis in cropping soil. The concentration of boron in cultivated soil in different agroecological regions was found to be low to very low (1mg/kg of soil) in this review study, which was undertaken to familiarize the status of boron in Nepalese cultivated land. In separate micronutrient investigations, a few additional micronutrients were shown to be medium albeit, boron was found to be low even in the valley (&gt;0.01ppm) including all three ecological regions. This shows boron deficiency is a universal problem in Nepal affecting 80-90% of agricultural soil. And this problem can be corrected by both foliar applications and by soil application of boron sources such as borate as per the recommended dose.

Reaction of Chalcones with Cellular Thiols. The Effect of the 4-Substitution of Chalcones and Protonation State of the Thiols on the Addition Process. Diastereoselective Thiol Addition.

Several biological effects of chalcones have been reported to be associated with their thiol reactivity. In vivo, the reactions can result in the formation of small-molecule or protein thiol adducts. Both types of reactions can play a role in the biological effects of this class of compounds. Progress of the reaction of 4-methyl- and 4-methoxychalcone with glutathione and N-acetylcysteine was studied by the HPLC-UV-VIS method. The reactions were conducted under three different pH conditions. HPLC-MS measurements confirmed the structure of the formed adducts. The chalcones reacted with both thiols under all incubation conditions. The initial rate and composition of the equilibrium mixtures depended on the ratio of the deprotonated form of the thiols. In the reaction of 4-methoxychalcone with N-acetylcysteine under strongly basic conditions, transformation of the kinetic adduct into the thermodynamically more stable one was observed. Addition of S-protonated N-acetylcysteine onto the polar double bonds of the chalcones showed different degrees of diastereoselectivity. Both chalcones showed a Michael-type addition reaction with the ionized and non-ionized forms of the investigated thiols. The initial reactivity of the chalcones and the equilibrium composition of the incubates showed a positive correlation with the degree of ionization of the thiols. Conversions showed systematic differences under each set of conditions. The observed differences can hint at the difference in reported biological actions of 4-methyl- and 4-methoxy-substituted chalcones.

Hydrophobic/Hydrophilic Interplay in 1,2,4‐Triazole‐ or Carboxylate‐Based Molybdenum(VI) Oxide Hybrids: A Step Toward Development of Reaction‐Induced Self‐Separating Catalysts

Abstract2‐(4H‐1,2,4‐triazol‐4‐yl)acetic acid (trglyH) and (dl)‐4‐methyl‐2‐(4H‐1,2,4‐triazol‐4‐yl)pentanoic acid (trleuH) were used as ligands for the development of MoO3 coordination hybrids for catalytic applications. Coordination polymers [Mo2O6(Htrgly)] ⋅ H2O (1) and [MoO3(trleuH)] ⋅ 0.5H2O (2) were prepared and structurally characterized. Compound 1 adopts a structure in which edge‐sharing MoO6 octahedra are organized in a ribbon motif via μ3‐O bridges. The Htrgly ligand exists as a zwitterion: −CO2− links two MoVI in a μ2‐η1 : η1 mode, while positively charged triazolium is left uncoordinated. In 2, Mo atoms are joined in a chain through μ2‐O. The more hydrophobic trleuH appears in a nonionized form and its [N−N] sites serve as a “clamp” for supporting the [−OMo(O)2−OMo(O)2(tr)2]n sequence. The complexes were explored for liquid phase catalytic epoxidation of cis‐cyclooctene, using H2O2 or tert‐butylhydroperoxide as oxidants. The hybrids showed good catalytic activity, and 2 behaved as a reaction‐induced self‐separating catalyst for olefin epoxidation with H2O2, presenting advantages of homogeneous and heterogeneous catalysis.

Effect of gold nanocomposite treatment on male reproductive function

Recently, it has been proved that polymers with a dextran core and grafted polyacrylamide chains dextran–polyacrylamide are effective in photodynamic chemotherapy, which gives confidence in the prospect of drug nanosystem. However, further research is needed to determine the effect of the treatment on male reproductive function. Experiments have been conducted on 50 male and 50 females Albino white laboratory mice (25–30 g). Copolymer dextran-graft-polyacrylamide in nonionic (D-g-PAA) and anionic forms (D-g-PAA(PE) was used as a polymer matrix for in situ synthesis of gold nanoparticles (AuNPs). D-g-PAA consists of dextran core and five grafted PAA chains. The copolymer in anionic form was prepared by alkaline hydrolysis. Polymer/AuNP systems contain AuNPs of 2–11 nm in size and have spherical shape. The treatment of substances was carried out in the following way: D-g-PAA and D-g-PAA(PE) (10,00 mg/kg), D-g-PAA/AuNPs and D-g-PAA(PE)/AuNPs (9.78 mg/kg), saline solution was introduced intravenously (in the tail vein, in 0.3 mL) once a day, five times. For the first time, it has been shown that treatment with D-g-PAA, D-g-PAA(PE), and D-g-PAA/AuNPs did not affect reproductive function in male mice. Disorder of the male reproductive function occurs under conditions of treatment with D-g-PAA(PE)/AuNPs. Significant changes in the values of were established in: (1) pre- and post-implantation mortality of embryos; (2) the number of live newborns (pups); (3) sperm and abnormal sperm forms (%); (4) spermatocytes (primary) and spermatids (%); (5) living, apoptotic and necrotic cells in the testis (spermatocytes (primary)) and in the epididymis (spermatozoa).

Comparative Analysis of Transformations of Heavy Oil Feedstock Model Components under Cracking Conditions in the presence of Metaland Acid Catalysts

The roles of a metal catalyst and hydrogen donors in thermal cracking were studied. The results were compared with those for a typical acid-type cracking catalyst (EMKAT). The role of the metal catalyst in thermal cracking was shown too consist of hydrogen-transfer reactions in mainly non-ionic forms. The ease of dehydrogenation of the hydrogen donor determined the degree of suppression of the cracking reactions.

Stabilization of glyphosate zwitterions and conformational/tautomerism mechanism in aqueous solution: insights from ab initio and density functional theory-continuum model calculations.

In this work, a comparative theoretical conformational analysis of the commercially most successful herbicide compound, glyphosate (N-phosphonomethylglycine), has been made at various quantum chemical levels of theory, in the gas phase and aqueous solution, using the integral equation-formalism polarizable continuum model (IEFPCM) and the solvation model density (SMD) approaches. The stable conformers of non-ionized (NE) and ionized or zwitterionic (ZW) neutral forms of glyphosate and the inter-conversions between them are described. Calculations revealed that several NE conformers of glyphosate exist in the gas phase but the zwitterionic form (ZW) is unstable in vacuo at all levels of theory. In aqueous solution, the stabilization of the zwitterion form of glyphosate was unable to be predicted satisfactorily within the equilibrated framework of the IEFPCM polarizable continuum model and using the standard UFF-radii cavity. However, the calculation with the density-based solvation model (SMD) was consistent with the experimental findings and led to the identification of the phosphonate zwitterionic (ZWP) structure as the global minimum energy in aqueous solution. The ZWP ⇋ NE tautomeric equilibrium between the non-ionized and zwitterionic forms of glyphosate was studied in aqueous solution at the SMD-B3LYP-D3/6-311++(2d,2p) level. Zwitterion formation in solution could occur by means of a concerted intramolecular proton transfer from the nitrogen to the oxygen of the phosphonate group. An analysis of the intermolecular mechanism shows that the addition of one water molecule favours the process either thermodynamically or kinetically. The possibility that the tautomerization process of glyphosate via a nonconcerted mechanism with zwitterion carboxylate (ZWC) as the intermediate can be excluded and the ZWP → ZWC proton transfer conversion can be a nearly barrierless process in PES and FES surfaces. comparison with similarly related biologically active systems was made.

Diatom-inspired self-assembly for silica thin sheets of perpendicular nanochannels

HypothesisMultistage silicate self-organization into light-weight, high-strength, hierarchically patterned diatom frustules carries hints for innovative silica-based nanomaterials. With sodium silicate in a biomimetic sol-gel system templated by a tri-surfactant system of hexadecyltrimethylammonium bromide, sodium dodecylsulfate, and poly(oxyethylene-b-oxypropylene-b-oxyethylene) (P123), mesoporous silica nanochannel plates with perpendicular channel orientation are synthesized. The formation process, analogous to that of diatom frustules, is postulated to be directed by an oriented self-assembly of the block copolymer micelles shelled with charged catanionic surfactants upon silication. ExperimentsThe postulated formation process for the oriented silica nanochannel plates was investigated using time-resolved small-angle X-ray and neutron scattering (SAXS/SANS) and freeze fracture replication transmission electron microscopy (FFR-TEM). FindingsWith fine-tuned molar ratios of the anionic, cationic, and nonionic surfactants, the catanionic combination and the nonionic copolymer form charged, prolate ternary micelles in aqueous solutions, which further develop into prototype monolayered micellar plates. The prolate shape and maximized surfactant adsorption of the complex micelles, revealed from combined SAXS/SANS analysis, are of critical importance in the subsequent micellar self-assembly upon silicate deposition. Time-resolved SAXS and FFR-TEM indicate that the silicate complex micelles coalesce laterally into the prototype micellar nanoplates, which further fuse with one another into large sheets of monolayered silicate micelles of in-plane lamellar packing. Upon silica polymerization, the in-plane lamellar packing of the micelles further transforms to 2D hexagonal packing of vertically oriented silicate channels. The unveiled structural features and their evolution not only elucidate the previously unresolved self-assembly process of through-thickness silica nanochannels but also open a new line of research mimicking free-standing frustules of diatoms.

Short chain fatty acids induced the type 1 and type 2 fimbrillin-dependent and fimbrillin-independent initial attachment and colonization of Actinomyces oris monoculture but not coculture with streptococci

BackgroundActinomyces oris is an early colonizer and has two types of fimbriae on its cell surface, type 1 fimbriae (FimP and FimQ) and type 2 fimbriae (FimA and FimB), which contribute to the attachment and coaggregation with other bacteria and the formation of biofilm on the tooth surface, respectively. Short-chain fatty acids (SCFAs) are metabolic products of oral bacteria including A. oris and regulate pH in dental plaques. To clarify the relationship between SCFAs and fimbrillins, effects of SCFAs on the initial attachment and colonization (INAC) assay using A. oris wild type and fimbriae mutants was investigated. INAC assays using A. oris MG1 strain cells were performed with SCFAs (acetic, butyric, propionic, valeric and lactic acids) or a mixture of them on human saliva-coated 6-well plates incubated in TSB with 0.25% sucrose for 1 h. The INAC was assessed by staining live and dead cells that were visualized with a confocal microscope.ResultsAmong the SCFAs, acetic, butyric and propionic acids and a mixture of acetic, butyric and propionic acids induced the type 1 and type 2 fimbriae-dependent and independent INAC by live A. oris, but these cells did not interact with streptococci. The main effects might be dependent on the levels of the non-ionized acid forms of the SCFAs in acidic stress conditions. GroEL was also found to be a contributor to the FimA-independent INAC by live A. oris cells stimulated with non-ionized acid.ConclusionSCFAs affect the INAC-associated activities of the A. oris fimbrillins and non-fimbrillins during ionized and non-ionized acid formations in the form of co-culturing with other bacteria in the dental plaque but not impact the interaction of A. oris with streptococci.