De novo transcriptome assembly of Aureobasidium melanogenum CGMCC18996 to analyze theβ-poly(L-malic acid)biosynthesis pathway under the CaCO_(3) addition

β-Poly(L-malic acid)(PMLA)is a water-soluble biopolymer used in food,medicine and other industries.To date,the biosynthesis pathway of PMLA has not been fully elucidated.In this study,we sequenced the transcriptom e of strain Aureobasidium melanogenum under 20 g/L CaCO_(3) addition.The resulting sequencing reads were assembled and annotated for the differentially expressed genes(DEGs)analysis and novel transcripts identification.The result indicated that with the CaCO_(3) addition,the tricarboxylic cycle(TCA)cycle and glyoxylate pathway were up-regulated,and it also found that a non-ribosomal peptide synthetase(NRPS)like protein was highly expressed.The DEGs analysis showed a high expression level of malate dehydrogenase(MDHC)and phosphoenolpyruvate carboxykinase(PCKA)in the CaCO_(3) group,which indicated a cytosolic malate activity.We speculated that the malate should be transported to or synthesized in the cytoplasm,which was then polymerized to PMLA by the NRPS-like protein,accompanied by the up-regulated TCA cycle providing ATP for the polymerization.Depending on the analysis,we assumed that an NRPS-like protein,the TCA cycle,and the cytosolic malate together are contributing to the PMLA biosynthesis.

Synthesis,Characterization and Antibacterial Properties of Rare Earth (Ce^(3+) ,Pr^(3+) ,Nd^(3+) ,Sm^(3+) ,Er^(3+) ) Complexes with L-Aspartic Acid and o-Phenanthroline

Five novel ternary complexes of rare earth ions with L-Aspartic acid (Asp) and o-phenanthroline (Phen) were synthesized in ethanol aqueous solution. Their compositions were characterized by elemental analysis, molar conductance, FT-IR, Raman, UV-VIS and TG-DTA. The compositions of the complexes were confirmed to be: RE( Asp)3PhenCl3·3H2O (RE: Ce3+ , Pr3+ , Nd3+ , Sm3+ , Er3+ ). The antibacterial activity test shows that all these complexes exhibit excellent antibacterial ability against Escherichia coli, Staphylococcus aureus and Candida albicans. The antimicrobial spectrum of the complexes are broad.

Electrocatalytic oxidation and determination of dopamine at a carbon ionic liquid electrode modified with nafion-L-aspartic acid composite film

The electrocatalytic oxidation of dopamine(DA)was studied by electrochemical approaches at a carbon ionic liquid electrode(CILE)modified with the composite film of nafion and L-aspartic acid(NL-CILE).The CILE was fabricated by replacing non-conductive organic binders with a room-temperature hydrophobic ionic liquid,1-butyl-3-methyl-imidazolium hexafluorophosphate.The composite film of NL was used as matrix to adsorb DA and catalyze the oxidation of DA in phosphate buffer solution(PBS).The electrochemical response of DA was investigated at the NL-CILE,the traditional carbon paste electrode(TCPE),CILE and the nafion modified CILE(N-CILE)in 0.1M PBS(pH 7.4),respectively.The results showed the superiority of NL-CILE to N-CILE,CILE and TCPE in terms of provision of higher sensitivity,faster electron transfer and better reversibility.Under optimum condition,the oxidation peak current was rectilinear with DA concentration range from 0.1μM to 0.1mM,with a detection limit of 0.03μM(S/N=3)by differential pulse voltammetry.The proposed method was applied to determine DA in samples successfully.

Preparation and enantiosorption of L-aspartic acid pillared hydrotalcites

L-aspartic acid （Asp） pillared hydrotalcites were prepared by direct reaction of the L-Asp anion with layered double hydroxides （LDHs）. The obtained samples were characterized by X-ray diffractometry （XRD）, Fourier transform infrared （FTIR）, and thermogravimetric and differential thermal analysis （TG/DTA）. The results show that the initial interlayer carbonate ions can be completely replaced by the L-Asp anion under the controlled conditions. The pillared hydrotalcites have a crystallized supramolecular structure and thermal stability. The L-Asp pillared LDHs were used in the enantiosorption of enantiopure phenylalanine （Pile）, the results suggest that L-Asp pillared LDHs exhibit an excellent enantiosorption capability for D-Phe, and the adsorption isotherm fits Freundlich equation.

Synthesis and Crystal Structure of a New Ternary Complex of Nickel(II) with L-Aspartic Acid and 1,10-Phenanthroline

A new ternary complex of nickel(II) with L-aspartate (L-Asp) and 1, 10-phenan- throline(Phen), [Ni3(L-Asp)(Phen)5(H2O)3](ClO4)4?4.75H2O, has been synthesized in a mixed sol- vent of H2OC2H5OH at the pH value of 3. It crystallizes in triclinic, space group P1 with a = 11.861(2), b = 18.384(4), c = 19.746(3) ?, α = 107.68(1), β = 105.94(1), γ = 103.41(2)°, V = 3703.6(11) ?3, Mr = 1745.66, Z = 2, Dc =1.565 g/cm3, μ = 0.989 mm-1, F(000) = 1791, R = 0.0643 and wR = 0.1611. The complex contains two cations, binuclear [Ni2(L-Asp)(Phen)3(H2O)]2+ and mononu- clear [Ni(Phen)2(H2O)2]2+. All the nickel ions in the complex are six-coordinated with a distorted octahedral geometry, but the coordination environments for them are different. There exist hydrogen bonds and π-π stacking interactions in the complex.

Investigation on interaction of L-aspartic acid with Vctoria Green S and its application

The interaction of L-Aspartic acid （Asp） with Vctoria Green S （VGS） in pH 6.0 Britton-Robinson buffer solution has been investigated by UV/Vis spectropbotometry and resonance light scattering （RLS） technique. The non-covalent interactions such as hydrogen bond, salt linkage and hydrophobic bond were proposed to explain the interaction between VGS and Asp. It indicated that Asp could link each other to form a long chain by salt linkages and hydrogen bonds in aqueous medium. Then the long chain surrounded the hydrophobic groups of VGS via hydrophobic interaction and reacted with VGS by salt linkages and hydrogen bonds to form a macromolecular aggregation. The aggregation was much bigger than VGS itself. So the color became deeper and the system＇s absorption and RLS intensity increased. The increase in the absorbance at 617nm was proportional to the concentration of Asp, providing a basis for the quantitative determination of Asp. This method was simple and efficient than the ordinary methods and had been applied to the direct determination of Asp with satisfactory results.

Selective Recognition and Detection of L-Aspartic Acid by Molecularly Imprinted Polymer in Aqueous Solution

Molecularly imprinted polymers selective for L-aspartic acid (LAA) have been prepared using the carboxy-betaine polymer bearing zwitterionic centres along the backbone. LAA is well known to promote good me-tabolism, treat fatigue and depression along with its significance in accurate age estimation in the field of forensic science and is an important constituent of ‘aspartame’, the low calorie sweetener. In order to study the intermolecular interactions in the prepolymerization mixture between the monomer and the template (LAA)/non-template (DAA), a computational approach was developed. It was based on the binding energy of the complex between the template and functional monomer. The results demonstrate that electrostatic in-teractions primarily guide the imprinting protocol. The MIP was able to selectively and specifically take up LAA from aqueous solution, human blood serum and certain pharmaceutical samples quantitatively. Hence, a facile, specific and selective technique to detect the amino acid, LAA in the presence of various interfer-rants, in different kinds of matrices is presented.

Synthesis of L-Aspartic Acid and Lactone Copolymers

Biodegradable poly(alc-alt-Asp) was synthesized by ring-opening polymerization of the monomer 3-(S)-[(benzyloxycarbonyl)methyl] -morpholine-2, 5-dione and subsequent catalytic hydrogenation. Copolymers of the monomer with glycolide, D,L-lactide and L-lactide were also prepared.

Synthesis and Hydrophilic Performance of Poly(Lactic Acid)-Poly(Ethylene Glycol) Block Copolymers

Lactide was synthesized using lactic acid and stannous octoate as raw material and catalyst, respectively. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was prepared by lactide and poly (ethylene glycol) (PEG) via ring-opening polymerization. The most appropriate technological conditions of synthesis of lactide were researched in the paper. The copolymers were measured by Infrared spectroscopy (IR) and 1H nuclear magnetic resonance (1H NMR). The results proved that the lactide and PLA-PEG were synthesized successfully. Hydrophilic performance of the copolymer was measured by a water contact angle tester after prepared into a flat membrane. The water contact angle changed from 81.5? to 71.6?, which proved that the hydrophily of PLA-PEG was better than PLA.

Microwave-assisted synthesis,crystal structure and toxicity of L-aspartic acid zinc spiral linear supramolecular polymer

L-aspartic acid zinc was synthesized by a rapid and convenient method in high yield under microwave conditions, and its single crystal structure was analyzed by X-ray diffraction. The structure unit of the title compound is [Zn(L-Asp)(H2O)2]·H2O, which is a bicyclo-complex forming a spiral linear polymer via coordination bonds. The spiral linear polymers are assembled as a three-dimensional supramolecule by intermolecular hydrogen bonds. The crystal belongs to the orthorhombic crystal system, P2(1)2(1)2(1) space group, a=0.7830(3) nm, b=0.9369(4) nm, c=11.599(5) nm, α=β=γ=90.00°, V=0.8509(6) nm3, Z=4, Dc=1.955 g/cm3, F(000)=512, μ=2.289. The toxicity of the title compound is lower than that of glutamic acid zinc and zinc sulfate. Keywords L-aspartic acid - zinc - microwave - supramolecule - toxicity

Combination of hydrophobically modified γ-poly(glutamic acid)and trehalose achieving high cryosurvival of RBCs

Trehalose is expected to be an alternative for toxic glycerol as a biocompatible cryoprotectant of red blood cells(RBCs).In this work,γ-poly(glutamic acid)(PGA)is modified by grafting hydrophobic phenethylamine,3,4-dimethoxyphenylethylamine and dodecylamine,respectively.The graft-modified PGA can significantly enhance cryosurvival of RBCs in combination with trehalose.Analyses of dynamic light scattering,hemolysis assay,atomic force microscope and confocal laser scanning microscope suggest that the modified PGA polymers can self-assemble into nanoparticles in phosphate buffer saline solutions at the pH range of 6.0–7.4,and exhibit membrane-disruptive activity due to hydrogen bond,conjugation and hydrophobic interactions with cell membranes.It is assumed that the modified PGA polymers can improve the cryosurvival of RBCs by promoting membrane permeability of trehalose.Among the three graft-modified polymers,phenethylamine-grafted PGA(PGA-g-PEA)can significantly increase the intracellular trehalose-loading content to 11.3±2.4 m M at pH 7.4,much higher than the value0.17±0.66 m M when trehalose is used without any polymers.In view of the aforementioned merit,the cryosurvival rate of sheep RBCs is increased to about 90%by incubation with 1.0 mg mL-1 PGA-g-PEA and 0.36 M trehalose.In vitro cell culture of L929 fibroblasts demonstrates low cytotoxicity of PGA-g-PEA.Therefore,hydrophobic PEA-modified PGA with enhanced intracellular trehalose-loading ability can be potentially applied in glycerol-free RBC cryopreservation or other related biomacromolecule delivery systems.

Polyelectrolyte complex micelles by self-assembly of polypeptide-based triblock copolymer for doxorubicin delivery

Polyelectrolyte complex micelles were prepared by self-assembly of polypeptide-based triblock copolymer as a new drug carrier for cancer chemotherapy.The triblock copolymer,poly(L-aspartic acid)-b-poly(ethylene glycol)-b-poly(L-aspartic acid)(PLD-b-PEG-b-PLD),spontaneously self-assembled with doxorubicin(DOX)via electrostatic interactions to form spherical micelles with a particle size of 60e80 nm(triblock ionomer complexes micelles,TBIC micelles).These micelles exhibited a high loading capacity of 70%(w/w)at a drug/polymer ratio of 0.5 at pH 7.0.They showed pH-responsive release patterns,with higher release at acidic pH than at physiological pH.Furthermore,DOX-loaded TBIC micelles exerted less cytotoxicity than free DOX in the A-549 human lung cancer cell line.Confocal microscopy in A-549 cells indicated that DOX-loaded TBIC micelles were transported into lysosomes via endocytosis.These micelles possessed favorable pharmacokinetic characteristics and showed sustained DOX release in rats.Overall,these findings indicate that PLDb-PEG-b-PLD polypeptide micelles are a promising approach for anti-cancer drug delivery.

Isolation and mechanism analysis of a catalytic efciency improved L‑aspartateβ‑decarboxylase toward 3‑methylaspartic acid

L-Aspartateβ-decarboxylase from Acinetobacter radioresistens(ArASD)has been modifed to convert 3-methylaspartic acid into 2-aminobutyric acid,which activated a novel process for biosynthesis of 2-aminobutyric acid.However,the process is limited by the low activity of the ArASD.Here,the activity of ArASD was signifcantly improved by modifcation based on sequence alignment and structural analysis.The 38th residue of ArASD is speculated to be the key residue for regulating the conformation of the internal aldimine,and site-directed mutagenesis on R38 residue was carried out.A variant,K18A/R38K/V287I,with 2.2 times higher specifc activity was isolated.Molecular dynamics simulation indicated that the torsion angle of the imine bond of the variant decreased,which was benefcial to the protonation of the internal aldimine and the increase in the initial energy of the enzyme.Therefore,the energy barrier of the transition state was reduced,resulting in improved catalytic activity toward 3-methylaspartic acid.These results provide a reference and a new point of view for enzyme modifcation by increasing the energy of the initial state.