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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Single-molecule fluorescence methods enable a new class of nucleic acid assays to be performed that are not possible with PCR-based methods. In this basic study, the methylene tetrahydrofolate reductase (MTHFR)-genotypes (normal, homozygous mutated, as well as heterozygous mutated) were directly detected for the first time onto unamplified double-stranded genomic DNA in solution down to femtomolar allele concentrations (10(-15) M) in a homogeneous assay format. This was accomplished by taking advantage of the decrease by a factor of 40 to 100 in fluorescence background signals of the non-bound nonlinear hybridization probes in two colors and two-color fluorescence cross-correlation spectroscopy. The designed 'intelligent' probes contained the built-in 5'-fluorescent dyes rhodamine green and Alexa633, respectively, and the 3'-non-fluorescent quenchers BHQ1 and BHQ3, respectively, with perfectly matched spectral overlaps for both dye-quencher combinations. Upon binding of two appropriate probes that were sequence-specific for the genotype, the steady-state fluorescence in two colors increased by about two orders of magnitude. The obtained allele sensitivity of femtomolar and the specificity of the described molecular interactions allow PCR-based allele distinction to be circumvented. Furthermore, the results present an alternative to existing hybridization approaches that are currently used with and without amplification at the 'many-molecule' level and the 'single-molecule' level.
Exp Mol Pathol 2005 Jun
PMID:A new ultrasensitive way to circumvent PCR-based allele distinction: direct probing of unamplified genomic DNA by solution-phase hybridization using two-color fluorescence cross-correlation spectroscopy. 1592 69

Four ligands 1,10-phenanthroline-5,6-bis(N,N-dibenzyl-1'-oxopropylamide) (La) 1,10-phenanthroline-5,6-bis(N-methyl-N-benzyl-1'-oxopropylamide) (Lb) 1,10-phenanthroline-5,6-bis(N-benzyl-1'-oxopropylamide) (Lc) and 1,10-phenanthroline-5,6-bis(N,N-diethyl-1'-oxopropylamide) (Ld), and their lanthanide(III) (La and Eu) complexes were synthesized. The complexes were characterized by elemental analysis, IR, fluorescence spectroscopy and conductivity. The lanthanide atoms are coordinated by O atoms from C=O, Ar-O -C and N atoms from phen With the difference of the ligands, the fluorescent intensities of the Eu(III) complexes vary regularly in the THF solution. Some factors that influence the fluorescent intensity were discussed.
Spectrochim Acta A Mol Biomol Spectrosc 2005 Dec
PMID:Terminal group effects on the fluorescence spectra of Eu(III) nitrate complexes with a family of amide-based 1,10-phenanthroline derivatives. 1595 63

We applied the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach to evaluate relative stability of the extended (flat) and C-shaped (bent) solution conformational forms of the 5,10-methylene-5,6,7,8-tetrahydrofolate (mTHF) molecule in aqueous solution. Calculations indicated that both forms have similar free energies in aqueous solution but detailed energy components are different. The bent solution form has lower intramolecular electrostatic and van der Waals interaction energies. The flat form has more favorable solvation free energy and lower contribution from the bond, angle and torsion angle molecular mechanical internal energies. We exploit these results and combine them with known crystallographic data to provide a model for the progressive binding of the mTHF molecule, a natural cofactor of thymidylate synthase (TS), to the complex forming in the TS-catalyzed reaction. We propose that at the time of initial weak binding in the open enzyme the cofactor molecule remains in a close balance between the flat and bent solution conformations, with neither form clearly favored. Later, thymidylate synthase undergoes conformational change leading to the closure of the active site and the mTHF molecule is withdrawn from the solvent. That effect shifts the thermodynamic equilibrium of the mTHF molecule toward the bent solution form. At the same time, burying the cofactor molecule in the closed active site produces numerous contacts between mTHF and protein that render change in the shape of the mTHF molecule. As a result, the bent solution conformer is converted to more strained L-shaped bent enzyme conformer of the mTHF molecule. The strain in the bent enzyme conformation allows for the tight binding of the cofactor molecule to the productive ternary complex that forms in the closed active site, and facilitates the protonation of the imidazolidine N10 atom, which promotes further reaction.
J Comput Aided Mol Des 2005 Feb
PMID:5,10-Methylene-5,6,7,8-tetrahydrofolate conformational transitions upon binding to thymidylate synthase: molecular mechanics and continuum solvent studies. 1607 6

The photophysical and photochemical properties of p-substitued 2-styryl-ethylbenzothiazolium iodides, possessing different electron-withdrawing or electron-donating groups are described. The dyes were prepared by the condensation of 3-ethyl-2-methylbenzothiazole salts with p-substituted benzaldehydes. The synthesis of suitable substrates is presented as well. We describe here the absorption, emission spectra and the luminescence quantum yield of hemicyanine dyes (SH) measured in 11 different organic solvents of varying polarity. Molecular structure of the synthesized dyes was established by (1)H NMR, electronic absorption and fluorescence spectrometry. The spectral data confirmed that all the compounds exist in E-configuration of their styryl residues. The planar molecular conformation is typical for the compounds with five-membered side aromatic moieties (for example benzothiazole). The compounds possessing N-alkyl substituent in phenyl ring, in contrast to the compounds with other substituents, exhibit low fluorescence quantum yield in THF solution. This indicates that for N-alkyl derivatives the non-radiative processes are much more effective than the radiative ones. The electronic absorption and fluorescence emission spectra of tested dyes demonstrate high sensitivity to the nature of substituent introduced into the aromatic ring.
Spectrochim Acta A Mol Biomol Spectrosc 2005 Nov
PMID:The synthesis and the solvent and substituent effect on the spectroscopic characteristic of 3-ethyl-2-(p-substitued styryl)benzothiazolium iodides. 1625 2

Umpolung catalysis is studied by a sequence of model reactions (CPCM in THF, B3LYP/6-31G*) with different aldehydes and catalysts. We involved addition of the catalyst to the aldehyde and 1,2-H-migration to form a carbanionic d1-species, which is the crucial intermediate according to the Lapworth- and Breslow-mechanisms. Cyanide, N-methylthiazol-2-ylidene, and a glycol-based phosphite perform as umpolung catalysts, formaldehyde, acetaldehyde, benzaldehyde, and acrolein are substrates in this study. In these aldehyde substrates, alkyl-substitution disfavors but pi-conjugation favors formation of the carbanionic d1-intermediate. The nucleophilic carbene, N-methylthiazol-2-ylidene, is the strongest umpolung catalyst, while the phosphite is about as active as cyanide.
J Mol Model 2006 Jul
PMID:Umpolung catalysts: comparative assessments on reactivities. 1625 39

The crystal structure of heterotetrameric sarcosine oxidase (TSOX) from Pseudomonas maltophilia has been determined at 1.85 A resolution. TSOX contains three coenzymes (FAD, FMN and NAD+), four different subunits (alpha, 103 kDa; beta, 44 kDa; gamma, 21 kDa; delta, 11 kDa) and catalyzes the oxidation of sarcosine (N-methylglycine) to yield hydrogen peroxide, glycine and formaldehyde. In the presence of tetrahydrofolate, the oxidation of sarcosine is coupled to the formation of 5,10-methylenetetrahydrofolate. The NAD+ and putative folate binding sites are located in the alpha-subunit. The FAD binding site is in the beta-subunit. FMN is bound at the interface of the alpha and beta-subunits. The FAD and FMN rings are separated by a short segment of the beta-subunit with the closest atoms located 7.4 A apart. Sulfite, an inhibitor of oxygen reduction, is bound at the FMN site. 2-Furoate, a competitive inhibitor with respect to sarcosine, is bound at the FAD site. The sarcosine dehydrogenase and 5,10-methylenetetrahydrofolate synthase sites are 35 A apart but connected by a large internal cavity (approximately 10,000 A3). An unexpected zinc ion, coordinated by three cysteine and one histidine side-chains, is bound to the delta-subunit. The N-terminal half of the alpha subunit of TSOX (alphaA) is closely similar to the FAD-binding domain of glutathione reductase but with NAD+ replacing FAD. The C-terminal half of the alpha subunit of TSOX (alphaB) is similar to the C-terminal half of dimethylglycine oxidase and the T-protein of the glycine cleavage system, proteins that bind tetrahydrofolate. The beta-subunit of TSOX is very similar to monomeric sarcosine oxidase. The gamma-subunit is similar to the C-terminal sub-domain of alpha-TSOX. The delta-subunit shows little similarity with any PDB entry. The alphaA domain/beta-subunit sub-structure of TSOX closely resembles the alphabeta dimer of L-proline dehydrogenase, a heteroctameric protein (alphabeta)4 that shows highest overall similarity to TSOX.
J Mol Biol 2006 Jul 28
PMID:Heterotetrameric sarcosine oxidase: structure of a diflavin metalloenzyme at 1.85 A resolution. 1682 Jan 68

Serine hydroxymethyltransferase (SHMT) catalyses the reversible conversion of serine and tetrahydrofolate to glycine and methylene-tetrahydrofolate. The recent completion of the genome sequence of Leishmania major revealed the presence of two genes coding for two isoforms of this protein. In silico analysis showed that one isoform had an extension at its N-terminus and was predicted to localize to the mitochondrion. The situation is different in other kinetoplastid parasites with only one SHMT encoding gene in Trypanosoma cruzi and no SHMT encoding gene in Trypanosoma brucei. The two L. major SHMT genes were cloned in frame with the green fluorescent protein and the resulting fusion proteins showed differential localization: the short form (SHMT-S) was found in the cytosol while the long one (SHMT-L) was found in an organelle that has hallmarks of the parasite mitochondrion. Indeed, SHMT-L had a similar cellular fractionation pattern as the mitochondrial HSP60 as determined by digitonin fractionation. Both SHMT-S and SHMT-L genes were expressed preferentially in the amastigote stage of the parasite and the RNA levels of SHMT-L could be modulated by glycine, serine, and folate. Overexpression of SHMT-S increased resistance to the antifolate methotrexate and to a lower level to the inhibitor thiosemicarbazide in a rich folate containing medium. These findings suggest that folate metabolism is compartmentalised in Leishmania and that SHMT RNA levels are responsive to environmental conditions.
Mol Biochem Parasitol 2006 Nov
PMID:Stage specific gene expression and cellular localization of two isoforms of the serine hydroxymethyltransferase in the protozoan parasite Leishmania. 1687 89

A novel 1,10-phenanthroline-containing p-conjugated chromophore, 3,8-di-(1-naphthyl)-1,10-phenanthroline, was synthesized by Suzuki reaction and its chelated complex was prepared. The UV-visible spectroscopy and photoluminescent (PL) properties were investigated. The results show that when the solution of the complex in THF located in low concentration range (<10(-6) mol/L), the fluorescence emission exhibit only one emission band and the excimer is formed with gradual increase in concentration of the complex. The emission spectra of the complex show obvious solvent effect. In addition, the intermolecular action between the complex and fullerene (C60) were investigated. The fluorescence intensity of the complex is decreased and the maximal emission obvious red-shifted with the increasing of the concentration of C60, which suggests that the strong interactions between the complex and C60 happen in the excited state.
Spectrochim Acta A Mol Biomol Spectrosc 2007 Apr
PMID:Synthesis and photophysical processes of a novel 1,10-phenanthroline-containing p-conjugated chromophores and Zn(II) chelated complex. 1713 38

A novel luminescent metal complex, (MQPF)3Al2, with 8-hydroxyquinoline aluminum and 9,9-diphenylfluorene was synthesized. The optical properties were investigated by UV-vis absorption and fluorescence emission spectra. The results showed that the luminescence quantum yield of (MQPF)3Al2 was 0.612 in THF and it emitted red light with the band gap of 3.18 eV estimated from the onset absorption. The emission spectra exhibited obvious solvent effect. With the increase of polarity of solvents the fluorescence spectra changed obviously and appeared blue shift about 60 nm at room temperature. In addition, the light-emitting can be quenched by both electron donor (N,N-dimethylaniline) and electron acceptor (Fullerene), where the processes followed the Stern-Volmer equation. However, when adding 1,4-dicyanobenzene (DCB) which was a stronger electron acceptor to the solution of (MQPF)3Al2, the fluorescent intensity was increased.
Spectrochim Acta A Mol Biomol Spectrosc 2007 Nov
PMID:Synthesis and photophysics of novel 8-hydroxyquinoline aluminum metal complex with fluorene units. 1739 26

From a library of 3,000 expression sequence tags (ESTs), derived from the epidermis of a diploid wheat (Triticum monococcum) inoculated with Blumeria graminis f. sp. tritici (Bgt), we cloned 23 cDNAs representing 12 genes that are involved in the pathways of biosynthesis and supply of methyl units. We studied the transcription of these genes to investigate how the methyl units are generated and regulated in response to Bgt infection and abiotic stresses in wheat. Expression of 5, 10-methylene-tetrahydrofolate reductase, methionine synthase, S-adenosylmethionine synthetase, and S-adenosylhomocystein hydrolase transcripts were highly induced at an early stage of infection. This induction was specific to the epidermis and linked to host cell wall apposition (CWA) formation, suggesting that the pathways for generation of methyl units are transcriptionally activated for the host defense response. Levels of S-adenosylmethionine decarboxylase, caffeic acid 3-O-methyltransferase, 1-aminocyclopropane-1-carboxylate oxidase mRNA, but not phosphoethanolamine N-methyltransferase and nicotianamine synthase mRNA, were up-regulated after infection and showed similar expression patterns to genes involved in the pathways of generation of methyl units, revealing possible routes of methyl transfer towards polyamine, lignin and ethylene biosynthesis rather than glycine betaine and nicotianamine in response to Bgt attack. After imposing various abiotic stresses, genes involved in the pathways of generation and supply of methyl units were also up-regulated differentially, suggesting that the generation of sufficient methyl units at an early stage might be crucial to the mitigation of multiple stresses.
Plant Mol Biol 2007 Jun
PMID:Transcriptional regulation of genes involved in the pathways of biosynthesis and supply of methyl units in response to powdery mildew attack and abiotic stresses in wheat. 1740 92


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