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1.
ACS Sens ; 8(12): 4625-4635, 2023 Dec 22.
Article in English | MEDLINE | ID: mdl-37992319

ABSTRACT

Although blood remains a gold standard diagnostic fluid for most health exams, it involves an unpleasant and relatively invasive sampling procedure (finger pricking or venous draw). Saliva contains many relevant and useful biomarkers for diagnostic purposes, and its collection, in contrast, is noninvasive and can be obtained with minimal effort. Current saliva analyses are, however, achieved using chromatography or lateral flow assays, which, despite their high accuracy and sensitivity, can demand expensive laboratory-based instruments operated by trained personnel or offer only semiquantitative results. In response, we investigated electrochemical aptamer-based (E-AB) biosensors, a reagentless sensing platform, to allow for continuous and real-time measurements directly in undiluted, unstimulated human whole saliva. As a proof-of-concept study, we developed E-AB biosensors capable of detecting low-molecular-weight analytes (glucose and adenosine monophosphate (AMP)). To our knowledge, we report the first E-AB sensor for glucose, an approach that is inherently independent of its chemical reactivity in contrast to home glucometers. For these three sensors, we evaluated their figures of merits, stability, and reusability over short- and long-term exposure directly in saliva. In doing so, we found that E-AB sensors allow rapid and convenient molecular measurements in whole saliva with unprecedented sensitivities in the pico- to nanomolar regime and could be regenerated and reused up to 7 days when washed and stored in phosphate-buffered saline at room temperature. We envision that salivary molecular measurements using E-AB sensors are a promising alternative to invasive techniques and can be used for improved point-of-care clinical diagnosis and at-home measurements.


Subject(s)
Aptamers, Nucleotide , Biosensing Techniques , Humans , Saliva/chemistry , Aptamers, Nucleotide/chemistry , Electrochemical Techniques/methods , Biosensing Techniques/methods , Glucose/analysis
2.
Chem Asian J ; 17(5): e202200013, 2022 Mar 01.
Article in English | MEDLINE | ID: mdl-35020275

ABSTRACT

The chemoselective hydroboration of aldehydes and ketones, catalyzed by Zinc(II) complexes [κ2 -(PyCH=NR)ZnX2 ] [R=CPh3 , X=Cl (1) and R=Dipp (2,6-diisoropylphenyl) and X=I (2)], in the presence of pinacolborane (HBpin) at ambient temperature and under solvent-free conditions, which produced the corresponding boronate esters in high yield, is reported. Zinc metal complexes 1 and 2 were derived in 80-90% yield from the reaction of iminopyridine [PyCH=NR] with anhydrous zinc dichloride in dichloromethane at room temperature. The solid-state structures of both zinc complexes were confirmed using X-ray crystallography. Zinc complex 1 was also used as a competent pre-catalyst in the reductive amination of carbonyl compounds with HBpin under mild and solvent-free conditions to afford a high yield (up to 97%) of the corresponding secondary amines. The wider substrate scope of both reactions was explored. Catalytic protocols using zinc as a pre-catalyst demonstrated an atom-economic and green method with diverse substrates bearing excellent functional group tolerance. Computational studies established a plausible mechanism for catalytic hydroboration.


Subject(s)
Amines , Zinc , Amination , Amines/chemistry , Catalysis , Ketones/chemistry
3.
Biotechnol Appl Biochem ; 69(3): 920-929, 2022 Jun.
Article in English | MEDLINE | ID: mdl-33830536

ABSTRACT

Ex vivo interaction of NaYF4 :Yb,Er nanophosphors with isolated mitochondria has been investigated. The nanophosphors were synthesized using the hydrothermal method. The synthesized NaYF4 :Yb,Er nanophosphors were characterized for physicochemical properties. The NaYF4 :Yb,Er nanophosphors showed successful upconversion with excitation wavelength lying in the near-infrared region. The effect of synthesized NaYF4 :Yb,Er nanophosphors on mitochondria isolated from the chicken heart tissue was examined through ROS generation capacity, membrane fluidity, and complex II activity. The exposer of NaYF4 :Yb,Er nanophosphors to isolated mitochondria inhibits ROS generation activity as compared to control. The mitochondria membrane fluidity of the lipid bilayer and complex-II activity of mitochondria was observed to be unaltered after the interaction with NaYF4 :Yb,Er nanoparticles. The results confirm that synthesized NaYF4 :Yb,Er nanoparticles can be used as a safe contrast agent.


Subject(s)
Erbium , Ytterbium , Erbium/chemistry , Fluorides/chemistry , Fluorides/pharmacology , Mitochondria , Reactive Oxygen Species , Ytterbium/chemistry , Yttrium/chemistry
4.
Environ Sci Pollut Res Int ; 29(14): 20048-20063, 2022 Mar.
Article in English | MEDLINE | ID: mdl-33761072

ABSTRACT

Frying affects the nutritional quality of fish detrimentally. In this study, using Catla catla and mustard oil, experiments were carried out in varying temperatures (140-240 °C), times (5-20 min), and oil amounts (25-100 ml/kg of fish) which established drastic reduction of 44.97% and 99.40% for polyunsaturated fatty acid (PUFA)/saturated fatty acids (SFA) and index of atherogenicity (IA) profile, respectively. Artificial neural network (ANN) was implemented successfully to provide an association between the independent inputs with dependent outputs (values of R2 were 0.99 and 0.98; RMSE were 0.038 and 0.046; and performance were 0.038 and 0.067 for PUFA/SFA and IA, respectively) by exhaustive search of various algorithms and activation functions available in literature. ANN model-based meta-heuristic, stochastic optimization formalisms, genetic algorithm (GA) and particle swarm optimization (PSO), were applied to optimize the combination of cooking parameters for improving the nutritional quality of food which improved the nutritional value by maximizing the PUFA/SFA profile up to 63.05% and minimizing the IA profile to 99.64%. Multi-objective genetic algorithm (MOGA) was also employed to tune the inputs by maintaining a balance between the contrasting outputs and enhance the overall food value simultaneously with multi-objective (beneficial for health, economic, and environment-friendly) proposal. MOGA was able to improve the PUFA/SFA profile up to 44.76% and reduce the IA profile to 92.94% concurrently with the reduction of wastage of culinary media and energy consumption, following the optimized cooking condition (118.92 °C, 6.06 min, 40 ml oil/kg of fish).


Subject(s)
Artificial Intelligence , Fatty Acids, Unsaturated , Animals , Fatty Acids , Neural Networks, Computer , Nutritive Value
5.
J Biomol Struct Dyn ; 40(9): 4100-4109, 2022 06.
Article in English | MEDLINE | ID: mdl-33272099

ABSTRACT

The 3D structure analysis for Muga silk protein was predicted through homology modeling and Ramachandran plot with the determination of quality index for Stereo/packing and 3D quality index. Silk Nanoparticles were synthesized using conventional desolvation and microwave-assisted radiolysis method from Muga silk fibroin. The secondary structure evolution due to two different synthesis methods was investigated using FTIR and Circular Dichroism (CD) spectroscopy. The microwave synthesized nanoparticles showed enhanced ß-sheet content than desolvation synthesized nanoparticles. The conformational changes of Muga silk fibroin protein to nanoparticle followed an ordered transition from random coil to α-helix then from α-helix to ß-turn and from ß-turn to ß-sheets where α-helix and ß-turn are the intermediate forms before getting stabilized to the metastable ß-sheets structure. The thermodynamics involved in secondary structure evolution was studied from CD analysis and activation energy involved in the formation of the secondary structure was determined. Communicated by Ramaswamy H. Sarma.


Subject(s)
Fibroins , Nanoparticles , Acetone , Fibroins/chemistry , Microwaves , Nanoparticles/chemistry , Silk/chemistry , Spectroscopy, Fourier Transform Infrared
6.
Biotechnol Appl Biochem ; 69(1): 129-135, 2022 Feb.
Article in English | MEDLINE | ID: mdl-33349956

ABSTRACT

The recent emergence of natural biopolymers as drug delivery vehicles is attributed to their biodegradability and less systemic toxicity. Muga silk nanoparticles were prepared using microwave radiolysis method and were characterized by Fourier transform infrared spectroscopy, circular dichroism, X-ray diffraction and transmission electron microscopy. To find the applicability in the drug delivery system of these nanoparticle and to know the binding site(s), a computational study was carried out. The structure of the Muga protein is predicted using homology modeling, which is further used for molecular docking. The in silico molecular docking between the Muga silk nanoparticles and three United States Food and Drug Administration-approved model drugs of doxorubicin, remdesivir and dexamethasone was performed. The binding capabilities and binding energy of the Muga silk proteins with these drugs are determined. The basic idea of the active site and the residues involved in the binding of the drugs/ligands is also studied. Doxorubicin showed the highest binding affinity of -8.7 kcal/mol and that of the remdesivir and dexamethasone are found to be -7.2 and -7.9 kcal/mol, respectively. Such high binding affinity(ies) would help for slow drug release kinetics and the other two drugs can be loaded when the requirement is for sustained drug release. The data were also validated using the UV-vis. spectroscopy.


Subject(s)
Nanoparticles , Pharmaceutical Preparations , Drug Liberation , Molecular Docking Simulation , Silk , Spectroscopy, Fourier Transform Infrared
7.
Org Biomol Chem ; 19(30): 6571-6587, 2021 Aug 05.
Article in English | MEDLINE | ID: mdl-34231617

ABSTRACT

Researchers around the globe have witnessed several breakthroughs in s- and p-block metal chemistry. Over the past few years, several applications in catalysis associated with these main group metals have been established, and owing to their abundance and low cost and they have proved to be essential alternatives to transition metal catalysts. In this review, we present a detailed discussion on the catalytic addition of P-H bonds from various phosphine reagents to multiple bonds of unsaturated substrates for the synthesis of organophosphorus compounds with C-P bonds promoted by various s- and p-block metal catalysts, as published in the last decade.

8.
J Membr Biol ; 254(2): 217-237, 2021 04.
Article in English | MEDLINE | ID: mdl-33786641

ABSTRACT

The paper assessed the toxic effect of titanium dioxide (TiO2) nanoparticles (NPs) on isolated mitochondria and its dysfunction prevention after Iron (Fe) incorporation. TiO2 and Fe content TiO2 NPs were synthesized and characterized using XPS, PL spectroscopy, and TEM. The nanostructure interaction with isolated mitochondria was investigated using circular dichroism (CD) confocal microscopy, flow cytometry, atomic force microscopy (AFM), surface-enhanced Raman spectroscopy (SERS), and FT-IR spectroscopy via nonspecific pathway. Fe content TiO2 NPs helps to control the dissolution rate of parent nanomaterial of TiO2 on the mitochondrial membrane. Confocal micrographs and flow cytometry results confirmed that Rhodamine 123 dye intensity get increased after interaction with Fe content TiO2 NPs which states the integrity of the mitochondrial membrane. AFM results revealed that TiO2 induces the swelling of mitochondrial tubules and also impaired the mitochondrial structure, whereas Fe content TiO2 NPs interaction prevents the impairment of mitochondrial tubules. The denaturation of a membrane protein by TiO2 interactions was observed through CD Spectroscopy. Further, nano-bio-interface study was performed using SERS, through shifting and extinct of peaks affiliated to membrane proteins and lipids. However, Fe content TiO2-treated samples showed a significant increase in the membrane potential of mitochondria via flow cytometry results.


Subject(s)
Iron , Membrane Potential, Mitochondrial , Mitochondria/drug effects , Nanoparticles , Titanium , Iron/chemistry , Nanoparticles/toxicity , Spectroscopy, Fourier Transform Infrared , Titanium/toxicity
9.
Biotechnol Appl Biochem ; 68(2): 345-355, 2021 Apr.
Article in English | MEDLINE | ID: mdl-32335949

ABSTRACT

Muga silk nanoparticles (MSNP) were synthesized using a microwave-assisted radiolysis method. The effect of microwave on the Muga protein secondary structures was analyzed. The evolution of the secondary structure from random coils to the ß-sheets was determined by using FTIR, circular dichroism and X-ray diffraction techniques. The results showed that Muga silk fibroin protein contained the primary structure in silk-I state. When the protein was irradiated with microwave, nanoparticle synthesis was possible having silk-II state imparting crystallinity. The silk nanoparticles were characterized by a particle size analyzer and found to be of ~240 nm in size. The optical properties of these nanoparticles were studied by UV-vis. spectroscopy and photoluminescence. For studying thermal properties, differential scanning calorimetry was performed that revealed early glass transition, which could be attributed to the presence of water and proteins. It also revealed that nanoparticles are thermally stable. Such studies are important for understanding more about the MSNP and would be beneficial for their further wide applications.


Subject(s)
Microwaves , Nanoparticles/chemistry , Silk/chemistry , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform Infrared , X-Ray Diffraction
10.
Org Biomol Chem ; 18(22): 4231-4237, 2020 06 10.
Article in English | MEDLINE | ID: mdl-32458962

ABSTRACT

Amidines are a preeminent group of organic compounds having wide applications in various industries. Here, we have developed a simple one-step reaction protocol for the facile synthesis of N-arylamidines catalysed by calcium bis(hexamethyldisilazide) [Ca{N(SiMe3)2}2(THF)2]. The amidine synthesis was readily achieved from organic nitriles and amines which provided a broad substrate scope ranging from electron-withdrawing to electron-donating substitutions as well as heterocyclic substitution. The reaction was carried out in a solvent-free medium under ambient conditions. The nucleophilic addition of aromatic amines to aryl nitriles led to good to excellent yields of the corresponding amidines. The reactivity of the amidines was further examined and the respective urea derivatives were achieved in excellent yields. The plausible mechanism involves the generation of an active calcium amido pre-catalyst that helps in the activation of nitriles in the reaction course.

11.
FEBS J ; 287(20): 4440-4457, 2020 10.
Article in English | MEDLINE | ID: mdl-32077246

ABSTRACT

Pro-islet amyloid polypeptide (proIAPP) is the prohormone precursor molecule to IAPP, also known as amylin. IAPP is a calcitonin family peptide hormone that is cosecreted with insulin, and largely responsible for hunger satiation and metabolic homeostasis. Amyloid plaques containing mixtures of mature IAPP and misprocessed proIAPP deposit on, and destroy pancreatic ß-cell membranes, and they are recognized as a clinical hallmark of type 2 diabetes mellitus. In order to better understand the interaction with cellular membranes, we solved the solution NMR structure of proIAPP bound to dodecylphosphocholine micelles at pH 4.5. We show that proIAPP is a dynamic molecule with four α-helices. The first two helices are contained within the mature IAPP sequence, while the second two helices are part of the C-terminal prohormone segment (Cpro). We mapped the membrane topology of the amphipathic helices by paramagnetic relaxation enhancement, and we used CD and diffusion-ordered spectroscopy to identify environmental factors that impact proIAPP membrane affinity. We discuss how our structural results relate to prohormone processing based on the varied pH environments and lipid compositions of organelle membranes within the regulated secretory pathway, and the likelihood of Cpro survival for cosecretion with IAPP. DATABASE: The assigned resonances have been deposited in the Biological Magnetic Resonance Bank (BMRB) with accession numbers 50007 and 50019 for proIAPP and Cpro, respectively. The lowest energy structures have been deposited in the Protein Data Bank (PDB) with access codes 6UCJ and 6UCK.


Subject(s)
Amyloid/chemistry , Proinsulin/chemistry , Humans , Hydrogen-Ion Concentration , Micelles , Molecular Dynamics Simulation , Nuclear Magnetic Resonance, Biomolecular , Protein Conformation
12.
Toxicol Res (Camb) ; 8(5): 711-722, 2019 Sep 01.
Article in English | MEDLINE | ID: mdl-31588348

ABSTRACT

The potential impact of TiO2 and Fe incorporated TiO2 nanoparticles at the organelle level has been reported. The toxicity of the samples on mitochondria isolated from chicken liver tissue has been examined through mitochondrial swelling, membrane fluidity, ROS generation capacity, and activity of complex II. The toxic effect of TiO2 was prevented by incorporating Fe into the TiO2 matrix at different concentrations. The activity of the succinate dehydrogenase enzyme complex was affected and permeabilization of the mitochondrial inner membrane to H+ and K+ and its alteration in membrane fluidity at 100 µg mL-1 of nano-TiO2 dosage were investigated, which showed significant changes in the anisotropy of DPH-labeled mitochondria. Fe incorporation into the TiO2 matrix makes it more biocompatible by changing its structure and morphology.

13.
Biointerphases ; 14(4): 041003, 2019 08 07.
Article in English | MEDLINE | ID: mdl-31390867

ABSTRACT

Titanium dioxide (TiO2) nanoparticles (NPs) have made unbelievable progress in the field of nanotechnology and biomedical research. The proper toxicological assessment of TiO2 NPs and the reduction of its cytotoxicity need to be addressed. Fe doping in TiO2 has been investigated to reduce the toxic effects of TiO2 NPs. Fe doped TiO2 powder samples were synthesized by sol-gel methods. The prepared samples were characterized by x-ray diffractometer (XRD), transmission electron microscope (TEM), and Raman spectroscopy to study their structure, morphology, and molecular conformation. XRD results revealed the coexistence of anatase (A) and rutile (R) phases of TiO2. The A-R transformation was observed with an increase in Fe doping along with the formation of α-Fe2O3 phase. TEM showed changes in morphology from spherical nanoparticles to elongated rod-shaped nanostructures with increasing Fe content. Shape variation of TiO2 nanoparticles after incorporation of Fe is a key reason behind the toxicity reduction. The authors observed that the toxicity of TiO2 nanoparticles was rescued upon Fe incorporation. The effect of NPs on the mitochondrial membrane potential (MMP) was assessed using flow cytometry. The MMP (%) decreased in TiO2 treated cells and increased by 1% Fe doped TiO2 NPs treated cells. Confocal imaging revealed the presence of functional mitochondria upon the exposure of Fe doped TiO2 NPs. The goal of the present study was to decrease the toxic effects induced by TiO2 NPs on mitochondrial potential and its prevention by Fe doping.


Subject(s)
Alloys/toxicity , Epithelial Cells/drug effects , Iron Compounds/toxicity , Membrane Potential, Mitochondrial/drug effects , Metal Nanoparticles/toxicity , Titanium/toxicity , Cell Line , Humans
14.
ACS Omega ; 4(7): 12470-12479, 2019 Jul 31.
Article in English | MEDLINE | ID: mdl-31460366

ABSTRACT

Engineering of water-dispersible Gd3+ ions-decorated reduced graphene oxide (Gd-rGO) nanosheets (NSs) has been performed. The multifunctional capability of the sample was studied as a novel contrast agent for swept source optical coherence tomography and magnetic resonance imaging, and also as an efficient drug-delivery nanovehicle. The synthesized samples were fabricated in a chemically stable condition, and efforts have been put toward improving its biocompatibility by functionalizing with carbohydrates molecules. Gd incorporation in rGO matrix enhanced the fluorouracil (5-FU) drug loading capacity by 34%. The release of the drug was ∼92% within 72 h. Gd-rGO nanosheets showed significant contrast in comparison to optically responsive bare GO for swept source optical coherence tomography. The longitudinal relaxivity rate (r 1) of 16.85 mM-1 s-1 for Gd-rGO was recorded, which was 4 times larger than that of the commercially used clinical contrast agent Magnevist (4 mM-1 s-1) at a magnetic field strength of 1.5 T.

15.
Dig Dis Sci ; 64(7): 1923-1928, 2019 07.
Article in English | MEDLINE | ID: mdl-30725303

ABSTRACT

BACKGROUND: Inflammatory bowel disease (IBD; Crohn's disease, CD and Ulcerative colitis, UC) and irritable bowel syndrome (IBS) have overlapping symptoms. Few prevalence studies of IBS in quiescent IBD have used colonoscopy with histology to confirm inactive disease. The aims were (1) to determine the percentage of IBD patients in deep remission whose persistent IBS-like symptoms (IBD/IBS+) would cause them to be classified as having active disease, based on the calculation of Harvey Bradshaw Index (HBI) or UC disease activity index (UCDAI); (2) to identify demographic and disease characteristics that are associated with IBD/IBS+. METHODS: This was a prospective study at a single tertiary care IBD center. 96/112 patients with colonoscopy and histology confirmed quiescent disease consented and completed Rome III criteria for IBS Survey, and the hospital anxiety and depression scale (HADS). Other demographic and disease specific data were collected. RESULTS: 36% (28/77) and 37% (7/19) of CD and UC patients, respectively, met diagnostic criteria for IBS. Significantly higher HBI/UCDAI scores (p = 0.005) and low short inflammatory bowel disease questionnaire (SIBDQ) scores (p ≤ 0.0001) were seen in IBD/IBS+ patients. 29% of patients in deep remission were mis-categorized by HBI/UCDAI as having active disease when they fulfilled Rome III criteria for IBS. Psychiatric diagnosis (OR 3.53 95% CI 1.2-10.2) and earlier onset of IBD (OR 1.056 95% CI 1.015-1.096) were associated with IBD/IBS+. Patients fulfilling IBS criteria had higher hospital anxiety and depression scale (HADS). CONCLUSION: IBD/IBS+ affect scoring of IBD disease activity scales and become less useful in guiding treatment plans.


Subject(s)
Anxiety/epidemiology , Colitis, Ulcerative/epidemiology , Crohn Disease/immunology , Depression/epidemiology , Irritable Bowel Syndrome/epidemiology , Adolescent , Adult , Anxiety/diagnosis , Anxiety/psychology , Biological Products/therapeutic use , Biopsy , Colitis, Ulcerative/diagnosis , Colitis, Ulcerative/drug therapy , Colonoscopy , Crohn Disease/diagnosis , Crohn Disease/drug therapy , Depression/diagnosis , Depression/prevention & control , Female , Humans , Immunosuppressive Agents/therapeutic use , Irritable Bowel Syndrome/diagnosis , Male , Middle Aged , Prevalence , Prognosis , Prospective Studies , Remission Induction , Risk Factors , Surveys and Questionnaires , Wisconsin/epidemiology , Young Adult
16.
Protein Pept Lett ; 26(4): 287-300, 2019.
Article in English | MEDLINE | ID: mdl-30666904

ABSTRACT

BACKGROUND: Human Serum Albumin (HSA) is the most abundant protein present in human blood plasma. It is a large multi-domain protein with 585 amino acid residues. Due to its importance in human body, studies on the interaction of HSA with different external agent is of vital interest. The denaturation and renaturation of HSA in presence of external agents are of particular interest as they affect the biological activity of the protein. OBJECTIVE: The objective of this work is to study the domain-specific and overall structural and dynamical changes occurring to HSA in the presence of a denaturing agent, urea and a renaturing agent, sucrose. METHODS: In order to carry out the domain-specific studies, HSA has been tagged using N-(7- dimethylamino-4-methylcoumarin-3-yl) iodoacetamide (DACIA) at Cys-34 of domain-I and pnitrophenyl coumarin ester (NPCE) at Tyr-411 site in domain-III, separately. Steady-state absorption, emission and solvation dynamic measurements have been carried out in order to monitor the domain-specific alteration of HSA caused by the external agents. The overall structural change of HSA have been monitored using circular dichroism spectroscopy. RESULTS: The α-helicity of HSA was found to decrease from 65% to 11% in presence of urea and was found to further increase to 25% when sucrose is added, manifesting the denaturing and renaturing effects of urea and sucrose, respectively. The steady state studies show that domain-III is more labile towards denaturation as compared to domain-I. The presence of an intermediate state is observed during the denaturation process. The stabilization of this intermediate state in presence of sucrose is attributed as the reason for the stabilization of HSA by sucrose. From solvation dynamics studies, it could be seen that the solvation time of DACIA inside domain-I of HSA decreases and increases regularly with increasing concentrations of urea and sucrose, respectively, while in the case of NPCE-tagged domain-III, the effect of sucrose on solvation time is evident only at high concentrations of urea. CONCLUSION: The denaturing and renaturing effects of urea and sucrose could be clearly seen from the steady state studies and circular dichroism spectroscopy measurements. A regular change in solvation time could only be observed in the case of domain-I and not in domain-III. The results indicate that the renaturing effect of sucrose on domain-III is not very evident when protein is in its native state, but is evident in when the protein is denatured.


Subject(s)
Models, Molecular , Serum Albumin, Human/chemistry , Sucrose/chemistry , Binding Sites , Humans , Kinetics , Protein Binding , Protein Conformation , Protein Stability
17.
Inorg Chem ; 57(20): 12610-12623, 2018 Oct 15.
Article in English | MEDLINE | ID: mdl-30259733

ABSTRACT

A series of mononuclear titanium(IV) complexes with the general composition κ3-[R{NHPh2P(X)}2Ti(NMe2)2] [R = C6H4, X = Se (3b); R = trans-C6H10, X = S (4a), Se (4b)] and [{κ2-N(PPh2Se)2}2Ti(NMe2)2] (6b) and two dinuclear titanium(IV) complexes, [C6H4{(NPh2PS)(N)}Ti(NMe2)]2 (3c) and [{κ2-N(PPh2Se)}Ti(NMe2)2]2 (6c), are reported. Dinuclear titanium(IV) complex 6c acts as an efficient catalyst for the chemoselective addition of an E-H bond (E = N, O, S, P, C) to heterocumulenes under mild conditions. The catalytic addition of aliphatic and aromatic amines, alcohol, thiol, phosphine oxide, and acetylene to the carbodiimides afforded the corresponding hydroelemented products in high yield at mild conditions with a broader substrate scope. The catalytic efficiency of the dinuclear complex depends on the cooperative effect of the TiIV ions, the systematic variation of the intermetallic distance, and the ligand's steric properties of the complex, which enhances the reaction rate. Most interestingly, this is the first example of catalytic insertion of various E-H bonds into the carbodiimides using a single-site catalyst because only the titanium-mediated insertion of E-H into a C═N unsaturated bond is reported to date. The amine and alcohol insertion reaction with the carbodiimides showed first-order kinetics with respect to the titanium(IV) catalyst as well as substrates. A most plausible mechanism for hydroelementation reaction is also proposed, based on the spectroscopic data of the controlled reaction, a time-course study, and the Hammett plot.

18.
Appl Environ Microbiol ; 84(21)2018 11 01.
Article in English | MEDLINE | ID: mdl-30143507

ABSTRACT

The development of Acidithiobacillus ferrooxidans as a non-model host organism for synthetic biology is hampered by a lack of genetic tools and techniques. New plating and liquid-based selection methods were developed to improve the identification of transformed cell lines. Enabled by these methods, a hyperactive transposase was used to generate mutants with integrated genes for the expression of the superfolder green fluorescent protein (sfGFP) gene or a 2-keto decarboxylase (KDC) gene, which enabled the production and secretion of isobutyric acid (IBA). An inverse PCR method was used to identify the insertion sites of the KDC gene in several mutants, leading to the identification of a region on the chromosome that may be suitable for future genetic insertions. These results demonstrate that functional exogenous metabolic genes have been chromosomally integrated into A. ferrooxidans, and this advance will facilitate the future development of these cells for new biotechnology applications.IMPORTANCEAcidithiobacillus ferrooxidans is an iron- and sulfur-oxidizing chemolithoautotroph and is a key member of the microbial consortia used in industrial biomining applications. There is interest in exploiting these cells for other metal recovery applications as well as in developing them as unique nonmodel microbial cell factories. Plasmid-driven expression of exogenous genes has been reported, and homologous recombination has been used to knock out some gene expression. Here, new selection protocols facilitated the development of a transposition method for chromosomal integration of exogenous genes into A. ferrooxidans This greatly expands the available genetic toolbox, which will open the door to greater metabolic engineering efforts for these cells.


Subject(s)
Acidithiobacillus/genetics , Chromosomes, Bacterial/genetics , Genetic Engineering/methods , Transposases/metabolism , Acidithiobacillus/metabolism , Gene Expression Regulation, Bacterial , Mutagenesis, Insertional , Transposases/genetics
19.
Curr Opin Biotechnol ; 45: 144-155, 2017 06.
Article in English | MEDLINE | ID: mdl-28371651

ABSTRACT

Developing new feedstocks for the efficient production of biochemicals and biofuels will be a critical challenge as we diversify away from petrochemicals. One possible opportunity is the utilization of sulfide-based minerals in the Earth's crust. Non-photosynthetic chemolithoautotrophic bacteria are starting to be developed to produce biochemicals from CO2 using energy obtained from the oxidation of inorganic feedstocks. Biomining of metals like gold and copper already exploit the native metabolism of these bacteria and these represent perhaps the largest-scale bioprocesses ever developed. The metabolic engineering of these bacteria could be a desirable alternative to classical heterotrophic bioproduction. In this review, we discuss biomining operations and the challenges and advances in the engineering of associated chemolithoautotrophic bacteria for biofuel production. The co-generation of biofuels integrated with mining operations is a largely unexplored opportunity that will require advances in fundamental microbiology and the development of new genetic tools and techniques for these organisms. Although this approach is presently in its infancy, the production of biochemicals using energy from non-petroleum mineral resources is an exciting new biotechnology opportunity.


Subject(s)
Biotechnology/methods , Mining , Bacteria/metabolism , Biofuels , Metabolic Engineering , Metals/metabolism , Minerals/metabolism , Oxidation-Reduction , Sulfides/metabolism
20.
Phys Rev Lett ; 111(6): 061101, 2013 Aug 09.
Article in English | MEDLINE | ID: mdl-23971549

ABSTRACT

Stellar mass black holes (SMBHs), forming by the core collapse of very massive, rapidly rotating stars, are expected to exhibit a high density accretion disk around them developed from the spinning mantle of the collapsing star. A wide class of such disks, due to their high density and temperature, are effective emitters of neutrinos and hence called neutrino cooled disks. Tracking the physics relating the observed (neutrino) luminosity to the mass, spin of black holes (BHs) and the accretion rate (M) of such disks, here we establish a correlation between the spin and mass of SMBHs at their formation stage. Our work shows that spinning BHs are more massive than nonspinning BHs for a given M. However, slowly spinning BHs can turn out to be more massive than spinning BHs if M at their formation stage was higher compared to faster spinning BHs.

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