H NMR Investigation of the Electronic Structure of the Four-Iron Ferredoxin from the Hyperthermophilic Archaeon Thermococcus litoralis

1994 ◽  
Vol 116 (15) ◽  
pp. 6841-6849 ◽  
Author(s):  
Antonio Donaire ◽  
Carol M. Gorst ◽  
Z. H. Zhou ◽  
Michael W. W. Adams ◽  
Gerd N. La Mar
Keyword(s):  
Electronic Structure ◽  
Thermococcus Litoralis ◽  
Hyperthermophilic Archaeon ◽  
H Nmr

Characterization of a novel moderate-substrate specificity amino acid racemase from the hyperthermophilic archaeon Thermococcus litoralis

2021 ◽  
Author(s):  
Ryushi Kawakami ◽  
Chinatsu Kinoshita ◽  
Tomoki Kawase ◽  
Mikio Sato ◽  
Junji Hayashi ◽  
...  
Keyword(s):  
Amino Acid ◽  
Substrate Specificity ◽  
Enzyme Stability ◽  
Hyperthermophilic Archaea ◽  
Thermococcus Litoralis ◽  
Hyperthermophilic Archaeon ◽  
Aminobutyrate Aminotransferase ◽  
Chaperone Protein ◽  
Amino Acid Racemase

Abstract The amino acid sequence of the OCC_10945 gene product from the hyperthermophilic archaeon Thermococcus litoralis DSM5473, originally annotated as γ-aminobutyrate aminotransferase, is highly similar to that of the uncharacterized pyridoxal 5ʹ-phosphate (PLP)-dependent amino acid racemase from Pyrococcus horikoshii. The OCC_10945 enzyme was successfully overexpressed in Escherichia coli by co-expression with a chaperone protein. The purified enzyme demonstrated PLP-dependent amino acid racemase activity primarily toward Met and Leu. Although PLP contributed to enzyme stability, it only loosely bound to this enzyme. Enzyme activity was strongly inhibited by several metal ions, including Co2+ and Zn2+, and non-substrate amino acids such as l-Arg and l-Lys. These results suggest that the underlying PLP-binding and substrate recognition mechanisms in this enzyme are significantly different from those of the other archaeal and bacterial amino acid racemases. This is the first description of a novel PLP-dependent amino acid racemase with moderate substrate specificity in hyperthermophilic archaea.

scholarly journals High-affinity maltose/trehalose transport system in the hyperthermophilic archaeon Thermococcus litoralis.

1996 ◽  
Vol 178 (16) ◽  
pp. 4773-4777 ◽  
Author(s):  
K B Xavier ◽  
L O Martins ◽  
R Peist ◽  
M Kossmann ◽  
W Boos ◽  
...  
Keyword(s):  
Transport System ◽  
Thermococcus Litoralis ◽  
Hyperthermophilic Archaeon ◽  
High Affinity

scholarly journals Archaeal Binding Protein-Dependent ABC Transporter: Molecular and Biochemical Analysis of the Trehalose/Maltose Transport System of the Hyperthermophilic Archaeon Thermococcus litoralis

1998 ◽  
Vol 180 (3) ◽  
pp. 680-689 ◽  
Author(s):  
Reinhold Horlacher ◽  
Karina B. Xavier ◽  
Helena Santos ◽  
Jocelyne DiRuggiero ◽  
Marina Kossmann ◽  
...  
Keyword(s):  
Transport System ◽  
Signal Sequence ◽  
Binding Protein ◽  
Inducible Promoter ◽  
Transport Systems ◽  
Thermococcus Litoralis ◽  
Hyperthermophilic Archaeon ◽  
E Coli ◽  
Transmembrane Segments ◽  
Maltose Transport

ABSTRACT We report the cloning and sequencing of a gene cluster encoding a maltose/trehalose transport system of the hyperthermophilic archaeonThermococcus litoralis that is homologous to themalEFG cluster encoding the Escherichia colimaltose transport system. The deduced amino acid sequence of themalE product, the trehalose/maltose-binding protein (TMBP), shows at its N terminus a signal sequence typical for bacterial secreted proteins containing a glyceride lipid modification at the N-terminal cysteine. The T. litoralis malE gene was expressed in E. coli under control of an inducible promoter with and without its natural signal sequence. In addition, in one construct the endogenous signal sequence was replaced by the E. coli MalE signal sequence. The secreted, soluble recombinant protein was analyzed for its binding activity towards trehalose and maltose. The protein bound both sugars at 85°C with aKd of 0.16 μM. Antibodies raised against the recombinant soluble TMBP recognized the detergent-soluble TMBP isolated from T. litoralis membranes as well as the products from all other DNA constructs expressed in E. coli. Transmembrane segments 1 and 2 as well as the N-terminal portion of the large periplasmic loop of the E. coli MalF protein are missing in the T. litoralis MalF. MalG is homologous throughout the entire sequence, including the six transmembrane segments. The conserved EAA loop is present in both proteins. The strong homology found between the components of this archaeal transport system and the bacterial systems is evidence for the evolutionary conservation of the binding protein-dependent ABC transport systems in these two phylogenetic branches.

scholarly journals Electronic Structure, Spectroscopic (IR, Raman, UV-Vis, NMR), Optoelectronic, and NLO Properties Investigations of Rubescin E (C31H36O7) Molecule in Gas Phase and Chloroform Solution Using Ab Initio and DFT Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-22 ◽  
Author(s):  
Richard Arnaud Yossa Kamsi ◽  
Geh Wilson Ejuh ◽  
Fidèle Tchoffo ◽  
Pierre Mkounga ◽  
Jean-Marie Bienvenu Ndjaka
Keyword(s):  
Electronic Structure ◽  
Chloroform Solution ◽  
3D Analysis ◽  
Coupling Constant ◽  
Dft Methods ◽  
Reactivity Descriptors ◽  
H Nmr ◽  
Quantum Chemical Methods ◽  
Td Dft ◽  
Electric Susceptibility

Quantum chemical methods were used to study the electronic structure and some physicochemical properties of Rubescin E molecule. Good agreement with experiment was found for J3H-H coupling constant, IR, 1H NMR, and 13C NMR. The excitation energy and oscillator strength calculated by TD-DFT also complement with experiment. Large values were obtained for dipole moment, polarizability, first static hyperpolarizability, electric susceptibility, refractive index, and dielectric constant, meaning that Rubescin E has strong optical and phonon application and can be a good candidate as NLOs material. The 3D analysis of the title molecule leads us to the conclusion that electron can easily be transferred from furan to tetrahydrofuran ring. The global reactivity descriptors were evaluated. Mulliken, ESP, and NBO charges comparisons were carried out and described.

Studies of structure and dynamics in a nominally symmetric twisted amide by NMR and electronic structure calculations

2006 ◽  
Vol 84 (3) ◽  
pp. 421-428 ◽  
Author(s):  
Alex D Bain ◽  
Hao Chen ◽  
Paul H.M Harrison
Keyword(s):  
Electronic Structure ◽  
Nmr Spectra ◽  
Chemical Exchange ◽  
Electronic Structure Calculations ◽  
Amide Bond ◽  
Electronic Effects ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Structure Calculations ◽  
C Nmr

Amides that are twisted around the C—N bond show unusual spectroscopy and reactivity when compared with planar amides. The diacyl derivatives of 3,4,7,8-tetramethyl-2,5-dithioglycoluril are intriguing examples of this class, since the crystal structures show that the two acyl groups are twisted by different amounts on either side of the molecule owing to a combination of steric and electronic effects. However, the 1H NMR spectra in solution at room temperature exhibit only one acyl resonance, so there must be fast interconversion among pairs of equivalent structures of each compound. We have prepared a number of derivatives with different acyl groups, both on the glycoluril framework as well as on its dithio analogue. The chemical exchange in solution was slowed down sufficiently by cooling to see individual sites for only two compounds: the dithiodipivaloyl and the dithiodiadamantyl derivatives. The barriers were estimated at 41 kJ mol–1 for the dipivaloyl derivative and 45 kJ mol–1 for diadamantyl derivative. The results show that rotation around the twisted amide bond is slowed by both the steric size of the acyl group and the presence of the thioureido group vs. the ureido group in the glycoluril core. In the solid-state 13C NMR spectra, there is no evidence for any dynamics, even for the diacetyl derivative at ambient temperature. Electronic structure calculations predict a geometry for the dipivaloyl derivative very close to that observed in the crystal structure. These results indicate that the crystal confines, but does not distort the molecule. A mechanism for the exchange is proposed. The relevance of these results to the mechanism of Claisen-like condensations in diacylglycolurils is also discussed.Key words: 1H and 13C NMR, exchange, dynamics, CP/MAS, solids, line shape analysis, amides, twisted amides, atropisomers, glycoluril.

Electronic structure of low-spin six-coordinate iron(III) meso-tetrapropylchlorin complexes

2014 ◽  
Vol 18 (08n09) ◽  
pp. 778-791 ◽  
Author(s):  
Akira Ikezaki ◽  
Jyunpei Ono ◽  
Yoshiki Ohgo ◽  
Mari Fukagawa ◽  
Takahisa Ikeue ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ground State ◽  
Nmr Spectra ◽  
Spectroscopic Properties ◽  
H Nmr ◽  
Axial Ligands ◽  
Splitting Parameter ◽  
Nmr Signals ◽  
Electronic Ground ◽  
C Nmr

Low-spin iron(III) tetrapropylchlorins [ Fe ( T n PrC ) L 2]± (L = HIm, 1-MeIm, DMAP, CN-, 4-CNPy, tBuNC) adopt the dxy-type ground state regardless of the nature of axial ligands. Among the complexes examined, [ Fe ( T n PrC )( t BuNC )2]+ has shown quite unique spectroscopic properties as described below. (1) 1 H NMR signals were extremely broad as compared with those of other complexes. In particular, 5,20- CH 2(α) signal was too broad to detect. (2) No signals except C γ were observed in 13 C NMR spectra. (3) Tetragonal splitting parameter (|Δ|) estimated by the EPR g values at 4.2 K reached as much as 12.4 λ, which is the largest |Δ| value among all the low-spin iron(III) porphyrins and porphyrinoids reported previously. On the basis of these results, we have concluded that [ Fe ( T n PrC )( t BuNC )2]+ adopts the low-spin iron(III) with (dxz, dyz)4(dxy)1 electronic ground state at 4.2–30 K where the EPR spectra are taken, while it should be expressed as the low-spin Fe ( II ) chlorin π-radical cation [ Fe II ( T n PrC .)( t BuNC )2]+ at ambient temperature where the NMR spectra are taken.

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