Doublet Signal Research Articles

SelEXSIDE: Fast and Easy Measurement of Multiple-Bond 1H,13C Coupling Constants for Stereochemical Analysis

Long-range (1)H,(13)C coupling constants ((n)J(CH)) are underutilized parameters for stereochemical structure determination, primarily because they are not easy to measure. This report describes a rapid and easily interpreted method for the measurement of one or more (n)J(CH) values based on a (13)C band-selective EXSIDE (SelEXSIDE), which reduces experiment times from many hours down to a few minutes while allowing a simple and straightforward readout of (n)J(CH) values from the resulting in-phase doublet signal.

Rapid Transcriptional Pulsing Dynamics of High Expressing Retroviral Transgenes in Embryonic Stem Cells

Single cell imaging studies suggest that transcription is not continuous and occurs as discrete pulses of gene activity. To study mechanisms by which retroviral transgenes can transcribe to high levels, we used the MS2 system to visualize transcriptional dynamics of high expressing proviral integration sites in embryonic stem (ES) cells. We established two ES cell lines each bearing a single copy, self-inactivating retroviral vector with a strong ubiquitous human EF1α gene promoter directing expression of mRFP fused to an MS2-stem-loop array. Transfection of MS2-EGFP generated EGFP focal dots bound to the mRFP-MS2 stem loop mRNA. These transcription foci colocalized with the transgene integration site detected by immunoFISH. Live tracking of single cells for 20 minutes detected EGFP focal dots that displayed frequent and rapid fluctuations in transcription over periods as short as 25 seconds. Similarly rapid fluctuations were detected from focal doublet signals that colocalized with replicated proviral integration sites by immunoFISH, consistent with transcriptional pulses from sister chromatids. We concluded that retroviral transgenes experience rapid transcriptional pulses in clonal ES cell lines that exhibit high level expression. These events are directed by a constitutive housekeeping gene promoter and may provide precedence for rapid transcriptional pulsing at endogenous genes in mammalian stem cells.

In vivo detection of 13C isotopomer turnover in the human brain by sequential infusion of 13C labeled substrates

This study demonstrates the feasibility of simultaneously detecting human brain metabolites labeled by two substrates infused in a sequential order. In vivo 13C spectra of carboxylic/amide carbons were acquired only during the infusion of the second substrate. This approach allowed dynamic detection of 13C labeling from two substrates with considerably different labeling patterns. [2-13C]glucose and [U–13C6]glucose were used to generate singlet and doublet signals of the same carboxylic/amide carbon atom, respectively. Because of the large one-bond 13C–13C homonuclear J coupling between a carboxylic/amide carbon and an aliphatic carbon (∼50Hz), the singlet and doublet signals of the same carboxylic/amide carbon were well distinguished. The results demonstrated that different 13C isotopomer patterns could be simultaneously and distinctly measured in vivo in a clinical setting at 3T.

All-optical ultra-wideband doublet signal source based on the cross-gain modulation in a semiconductor optical amplifier

We propose a novel scheme to generate the ultra-wideband (UWB) doublet signal pulse based on the cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA). In the scheme, only an optical source and an SOA are needed. As there is only one wavelength included in the output doublet signal pulse, no time difference between the upper and down pulses is introduced during the transmission process. By using the software of Optisystem 7.0, the impacts of the optical power, the SOA current, the wavelength and the input signal pulse width on the generated doublet pulse are simulated and tudied numerically. The results show that when the pulse width of the input signal pulse is larger, the output signal pulse is better, and is insensitive to the change of wavelength. In addition, the ultra-wideband positive and negative monocycles can be generated by choosing suitable optical source power and SOA current.

Bismuth Nonlinear Optical Fiber for Photonic Ultrawideband Radio-Signal Processing

The feasibility of using a bismuth-oxide-based nonlinear optical fiber (Bi-NLF) for the implementation of ultrawideband (UWB) radio-signal-processing schemes is experimentally investigated. The use of two different types of nonlinear signal processors for the generation of UWB pulses is demonstrated. One processor uses cross-phase modulation for monocycle pulse generation, whereas the other uses nonlinear polarization rotation for doublet pulse generation. It is experimentally shown that UWB monocycle and doublet pulses can be successfully generated using the Bi-NLF-based nonlinear signal processors. Moreover, the system performance for the generation of UWB pulses is evaluated by performing a transmission experiment over a 20-km-long nonzero dispersion-shifted fiber (NZ-DSF) link. Error-free and penalty-free UWB doublet signal transmission is achieved.

All-optical pulse shaping for ultrawideband doublet pulses using nonlinear optical loop mirror with optical parametric amplification

We propose and experimentally demonstrate an alternative photonic scheme for the generation of ultrawideband (UWB) doublet pulses, which is based on an optical fiber-based nonlinear optical loop mirror (NOLM) incorporating the optical parametric amplification (OPA) effect. The proposed scheme uses both cross-phase modulation and OPA within an optical fiber-based NOLM to produce an ideal transfer function for the shaping of input soliton pulses into doublet pulses. Using the proposed scheme, a successful conversion of input soliton pulses into doublet pulses is readily demonstrated. The system performance of UWB doublet pulses is also assessed by propagating the 1.25 Gbit/s doublet pulses over a fiber link. Error-free UWB doublet signal transmission is demonstrated.

Pulsed EPR Analysis of the Photo-Induced Triplet Radical Pair in the BLUF Protein SyPixD: Determination of the Protein–Protein Distance and Orientation in the Oligomeric Protein

A photo-induced radical pair of FADH· and Y8· and in BLUF protein SyPixD was studied by pulsed electron paramagnetic resonance (EPR) spectroscopy. Blue light illumination at 150 K for 30 min followed by cooling to 50 K during illumination induced the stable radical pair. The EPR signal has been characterized by a Pake doublet signal with complete S = 1 spin state. The radical pair was utilized as a probe to analyze the oligomer of SyPixD. The relative arrangement of PixD proteins in the complex was investigated by pulsed electron–electron double resonance (PELDOR) with the orientation selection. Based on the decameric structure in the crystal, the possible structure for the PELDOR results was discussed.

Photonic Ultrawideband Pulse Generation With HNL-DSF-Based Phase and Intensity Modulator

We propose and experimentally demonstrate a photonic ultrawideband (UWB) pulse (monocycle and doublet) generator based on a highly nonlinear dispersion-shifted fiber (HNL-DSF). The pulsed pump, located in the anomalous group-velocity dispersion regime of the HNL-DSF, performs as both an intensity and a phase modulator in our scheme. We experimentally prove, for the first time to the best of our knowledge, that the UWB doublet pulse can be generated when the optical carrier is located at the center of a narrow tunable filter's passband. Furthermore, the encoded doublet signal, fully compliant with the Federal Communications Commission (FCC) regulations, is transmitted at 950 Mb/s through a 25-km single-mode fiber without introducing any obvious pulse distortion.

Synthesis and Antimicrobial Evaluation of Some New Tetrahydropyrimidine Derivatives

The utility of 1,2,3,4-tetrahydropyrimidine-5-carboxylate (1a,b), and 1,2-dihydropyrimidine-5-carboxylate (2) in the synthesis of some new functionalized pyrimidine derivatives such as 6-(2-(dimethylamino)vinyl)-1,2,3,4tetrahydropyrimidine, 6-(1-cyano-2-(phenylamino)-2-thioxoethyl)-1,2,3,4-tetrahydropyrimidine and 4,6-distyryl-1,2-dihydropyrimidine derivatives is reported. Antimicrobial evaluation of some selected examples from the synthesized products was carried out and showed promising results. Pyrimidine derivatives are reported to possess antibacterial, antifungal anticancer, antiinflammatory, and cardioprotective effects. In addition, certain pyrimidine derivatives are known to display antimalarial, antifilarial and antileshmainal activities. Also, pyrimidine nucleus is considered as one of the most important classes of chemotherapeutic drugs. Many pyrimidine derivatives are used for thyroid drugs and leukemia. In view of the these results and as an extension of our recent work concerned with the synthesis of heterocycles of interested biological activity we decided to synthesize some new pyrimidine derivatives starting from the readily obtainable 1,2,3,4-tetrahydropyrimidine-5-carboxylate derivatives 1a, 1b, and dihydropyrimidine 2 as highly versatile and useful building blocks for the synthesis of a wide variety of pyrimidine derivatives and to test their antimicrobial activity. 1,2,3,4-Tetrahydropyrimidine 1a was found to react readily with dimethylformamide dimethyl acetal (DMF-DMA) to produce ethyl 6-(2-(dimethylamino)vinyl)-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine5-carboxylate (3) (Scheme 1). The IR spectrum of the product 3 showed absorption bands at, 1624, 1701, 3117, 3244 cm due to two carbonyl groups, and two imino functions, respectively. Its H NMR spectrum showed a triplet signal at  1.11 (J = 6.9 Hz) due to CH3 protons, singlet signal at  2.85, characteristics for two methyl protons, a quartet signal at  3.96 (J = 6.9 Hz) due to CH2 protons, a doublet signal at  5.17 (J = 3.6 Hz) due to CH proton, two doublets at  6.18 and  7.48 (J = 14.1 Hz) due to two olefinic protons, and two D2O-exchangeable signals at  7.52 and 8.61 corresponding to two NH protons, in addition to an aromatic multiplet in the region  7.22-7.29. The value of the coupling constant for the ethylenic protons indicates that the pyrimidine 3 exists exclusively in the E-configuration.

Comparative EPR Study of Monomer and Polymerized Phases of C60

Temperature dependences of EPR spectra of the monomer, 1D (orthorhombic), and 2D (tetragonal and rhombohedral) polymerized phases of C60 were studied in the range of 11–295 K. It was shown that the concentration of paramagnetic centers depends radically on the type of polymerized phases. The temperature dependences allow one to separate temperature-dependent and temperature-independent components of the main doublet signals, which were attributed to C60 + radical and to conducting electrons, respectively. Additional triplet EPR signals assigned to dimer centers formed by a coupling of two C60 + radical were observed for the tetragonal and rhombohedral phases.

Ultrawideband Doublet Pulse Generation Based on a Semiconductor Electroabsorption Modulator and Its Distribution Over a Fiber/Wireless Link

An alternative photonic-generation scheme of ultrawideband (UWB) doublet pulses based on a semiconductor electroabsorption modulator (EAM) is proposed. The use of EAMs for doublet pulse generation has not been reported due to the difficulty of producing a U-shaped electrical-to-optical (E-O) transfer function. It is shown in the study that the creation of a U-shaped E-O transfer function from multi-quantum-well-based EAMs can be easily done under special conditions. An experiment is subsequently conducted to demonstrate the successful generation of UWB doublet pulses. The system performance of the generated UWB doublet pulses is then evaluated through a range of signal transmission experiments over a fiber/wireless transmission link. Error-free UWB doublet signal transmission is demonstrated.

EPR study of the crystalline polymerized phases of C60

AbstractComparative electron paramagnetic resonance (EPR) study of the monomer and 1D (orthorhombic) and 2D (tetragonal and rhombohedral) polymerized phases of C60 has been carried out. It was shown that the concentration of paramagnetic centers (PC) depends on the phase structure. Temperature dependences of the EPR spectra enabled separation of temperature‐dependent from temperature‐independent components of the main doublet signals, which were attributed to C radical (PC1) and to conducting electrons, respectively. Additional weak EPR signals, observed for the tetragonal and rhombohedral phases, were attributed to dimer PC2 formed by coupling of two PC1. Possible models for these centers are discussed.

Glycation Isotopic Labeling with 13C-Reducing Sugars for Quantitative Analysis of Glycated Proteins in Human Plasma

Non-enzymatic glycation of proteins is a post-translational modification produced by a reaction between reducing sugars and amino groups located in lysine and arginine residues or in the N-terminal position. This modification plays a relevant role in medicine and food industry. In the clinical field, this undesired role is directly linked to blood glucose concentration and therefore to pathological conditions derived from hyperglycemia (>11 mm glucose) such as diabetes mellitus or renal failure. An approach for qualitative and quantitative analysis of glycated proteins is here proposed to achieve the three information levels for their complete characterization. These are: 1) identification of glycated proteins, 2) elucidation of sugar attachment sites, and 3) quantitative analysis to compare glycemic states. Qualitative analysis was carried out by tandem mass spectrometry after endoproteinase Glu-C digestion and boronate affinity chromatography for isolation of glycated peptides. For this purpose, two MS operational modes were used: higher energy collisional dissociation-MS2 and CID-MS3 by neutral loss scan monitoring of two selective neutral losses (162.05 and 84.04 Da for the glucose cleavage and an intermediate rearrangement of the glucose moiety). On the other hand, quantitative analysis was based on labeling of proteins with [(13)C(6)]glucose incubation to evaluate the native glycated proteins labeled with [(12)C(6)]glucose. As glycation is chemoselective, it is exclusively occurring in potential targets for in vivo modifications. This approach, named glycation isotopic labeling, enabled differentiation of glycated peptides labeled with both isotopic forms resulting from enzymatic digestion by mass spectrometry (6-Da mass shift/glycation site). The strategy was then applied to a reference plasma sample, revealing the detection of 50 glycated proteins and 161 sugar attachment positions with identification of preferential glycation sites for each protein. A predictive approach was also tested to detect potential glycation sites under high glucose concentration.

EX VIVO ANALYSIS OF IRRADIATED FINGERNAILS: CHEMICAL YIELDS AND PROPERTIES OF RADIATION-INDUCED AND MECHANICALLY-INDUCED RADICALS

A qualitative and quantitative analysis of the radicals underlying the radiation-induced signal (RIS) in fingernails was conducted in an attempt to identify properties of these radicals that could be used for biodosimetry purposes. A qualitative analysis of RIS showed the presence of at least three components, two of which were observed at low doses (<50 Gy) and the third required higher doses (>500 Gy). The low dose signal, obtained by reconstruction, consists of a 10 gauss singlet at g = 2.0053 and an 18 gauss doublet centered at g = 2.0044. Based on the initial slope of the dose-response curve, the chemical (radical) yields of the radicals giving rise to the singlet and doublet were 327 (+/-113) and 122 (+/-9) nmol J-1 (standard error, SE), respectively. At doses below 50 Gy, the singlet signal is the dominant component. Above this dose range, the signal intensity of the singlet rapidly dose-saturates. At doses <50 Gy, there is a small contribution of the doublet signal that increases in its proportion of the RIS as dose increases. A third component was revealed at high dose with a spectral extent of approximately 100 gauss and displayed peaks due to g anisotropy at g = 2.056, 2.026, and 1.996. The total radical yield calculated from the initial slope of the dose-response curve averaged 458 +/- (116) nmol J-1 (SE) in irradiated nail clippings obtained from six volunteers. Such high yields indicate that nails are a strong candidate for biodosimetry at low doses. In a comparison of relative stabilities of the radicals underlying the singlet and doublet signals, the stability of the doublet signal is more sensitive to the moisture content of the nail than the singlet. This differential in radical stabilities could provide a method for removing the doublet signal under controlled exposures to high humidities (>70% relative humidity). The decay of the singlet signal in RIS varies with exposure of a nail clipping to differing ambient humidities. However, long exposures (>6 h) to relative humidities of 72-94% results in singlet intensities that approach 7.0 +/- (3.2)% (standard deviation) of the original intensities in an irradiated nail. This result suggests the existence of a subpopulation of radicals underlying the singlet signal that is relatively insensitive to decay under exposure of nails even to high humidities. Therefore, exposures of an irradiated nail clipping under controlled humidities may provide a method for estimating the exposure dose of the nail that is based on the intensity of the signal of the humidity insensitive radical population underlying the singlet signal.

3P277 ESEEM studies of the doublet signal with spin S = 1 in the blue light sensor BLUF protein SyPixD(Photobiology: Vision & Photoreception,The 48th Annual Meeting of the Biophysical Society of Japan)

3P277 ESEEM studies of the doublet signal with spin S = 1 in the blue light sensor BLUF protein SyPixD(Photobiology: Vision & Photoreception,The 48th Annual Meeting of the Biophysical Society of Japan)

A simple method of β-aminophosphonates synthesis

We developed a simple two-stage synthesis of aminophosphonates containing an unsubstituted amino group, whose synthesis by other methods was a complex problem [1, 2]. Diethyl methylphosphonate was treated by butyllithium in THF, after which it was reacted with nitriles to form β-enaminophosphonates Ia–Id in high yields as we have described previously [3]. Then βenaminophosphonates I were reduced with calcium borohydride in the THF-isopropanol or THF-aqueous ethanol mixture to give β-aminophosphonate II in high yield. Calcium borohydride was obtained by the reaction of sodium borohydride with calcium chloride in THF. In the mixture THF-aqueous ethanol this reaction proceeded more rapidly. However, besides aminophosphonate, ketophosphonate admixture formed (~10%), which was easily separated by extraction with ethyl acetate after acidification of the reaction mixture by hydrochloric acid where the aminophosphonate exists as hydrochloride. Free aminophosphonate was isolated after the reaction mixture was neutralized with alkali. Aminophosphonates were purified by vacuum distillation, and they were isolated as colorless viscous liquids. Purity and structure of aminophosphonates II were confirmed by TLC, Н, F, and Р NMR spectroscopy. In the P NMR spectrum the chemical shifts δP were displaced to 30 ppm. The Н NMR spectra contain a doublet signal of the two protons of PCH2 group; protons of amino group appear as a broad signal at 2.5 ppm.

Convergence of the 5-LOX and COX-2 pathways: heme-catalyzed cleavage of the 5S-HETE-derived di-endoperoxide into aldehyde fragments

Oxygenation of the 5-lipoxygenase product 5S-hydroxyeicosatetraenoic acid by cyclooxygenase-2 yields a bicyclic di-endoperoxide. The di-endoperoxide contains two peroxides spanning from carbons 9 to 11 and 8 to 12, and two hydroxyls at carbons 5 and 15 of arachidonic acid (Schneider C., et al. 2006. Convergent oxygenation of arachidonic acid by 5-lipoxygenase and cyclooxygenase-2. J. Am. Chem. Soc. 128: 720). Here, we report that treatment of the di-endoperoxide with hematin or ferrous chloride results in cleavage of both peroxide O-O bonds and of the bonds between the carbons that carry the peroxide groups, producing the aldehydes 4-hydroxy-2E-nonenal (4-HNE), 8-oxo-5S-hydroxy-6E-octenoic acid, and malondialdehyde (MDA). The hematin- and ferrous iron-catalyzed transformation of the di-endoperoxide proceeded with a similar yield of products as the cleavage of the prostaglandin endoperoxide PGH(2) to 12S-hydroxy-5Z,8E,10E-heptadecatrienoic acid and MDA. Chiral phase HPLC analysis of the 4-HNE cleavage product showed greater than 98% 4S and thus established the S configuration of the 15-carbon of the di-endoperoxide that had not previously been assigned. This transformation of the 5-lipoxygenase/cyclooxygenase-2 derived di-endoperoxide invokes the possibility of a novel pathway to formation of the classic lipid peroxidation products 4-HNE and MDA.

Hyperfine structure and electrochemical behavior of Fe-Cr-Ni alloys

With the use of nuclear γ-resonance Mossbauer spectroscopy, the hyperfine structure of quenched (1100° C, 1 h, water) Fe-∼20% Cr-(9.6, 40.8, 70.7)% Ni alloys is studied. With the Normos program package, the isomer (chemical) shift Γ (mm/s) of the singlet and doublet signals, the half-width Γ (mm/s) of the singlet and doublet spectral components, the area part S (%) of the components in the general spectra, and the probability distribution function of hyperfine magnetic fields P(Heff) are calculated. The effect of nickel on the electron density distribution around 57Fe nuclei is discovered. Novel data on the presence of ferromagnetic phases, their nuclei and clusters in Fe-19.6% Cr-9.6% Ni are obtained. The data of Mossbauer spectroscopy are compared to the anodic polarization curves recorded in a 1 N H 2SO4 solution with the aim to clarify the relation between the electronic structure and electrochemical behavior of alloys

Exchange coupled pairs of dangling bond spins as a new type of paramagnetic defects in nanodiamonds

EPR in detonation nanodiamonds (DND) reveals two different signals associated with intrinsic carbon inherited paramagnetic defects. Main carbon inherited EPR signal is narrow intensive Lorentzian-like singlet with g=2.0028 and spin concentration Ns=(6−7)×1019 spin/g that yields on average 13–15 spins per each DND particle. Additional chemical treatment of DND powder allows practically complete removal of trace amounts of transition metal impurities that reveals a new doublet EPR signal consisting of two relatively narrow lines within the half-field region (g∼4) separated by a distance of 10.4 mT. The intensity of the doublet signal is five orders of magnitude lower than that of the main singlet signal. The former signal has been observed in a wide variety of DND samples disregarding of the impurity level reached and thus may be attributed to some intrinsic defects in DND particles. Such half-field EPR signals correspond to “forbidden” ΔMs=2 transitions within thermally populated triplet (S=1) levels observed in polycrystalline samples containing exchange dimers—antiferromagnetically coupled spin pairs. Estimates suggest that the concentration of such defects is about one dimer per hundreds DND particles.

Peroxide-induced radical formation at TYR385 and TYR504 in human PGHS-1

Prostaglandin H synthase isoforms 1 and -2 (PGHS-1 and -2) react with peroxide to form a radical on Tyr385 that initiates the cyclooxygenase catalysis. The tyrosyl radical EPR signals of PGHS-1 and -2 change over time and are altered by cyclooxygenase inhibitor binding. We characterized the tyrosyl radical dynamics using wild type human PGHS-1 (hPGHS-1) and its Y504F, Y385F, and Y385F/Y504F mutants to determine whether the radical EPR signal changes involve Tyr504 radical formation, Tyr385 radical phenyl ring rotation, or both. Reaction of hPGHS-1 with peroxide produced a wide singlet, whereas its Y504F mutant produced only a wide doublet signal, assigned to the Tyr385 radical. The cyclooxygenase specific activity and K(M) value for arachidonate of hPGHS-1 were not affected by the Y504F mutation, but the peroxidase specific activity and the K(M) value for peroxide were increased. The Y385F and Y385F/Y504F mutants retained only a small fraction of the peroxidase activity; the former had a much-reduced yield of peroxide-induced radical and the latter essentially none. After binding of indomethacin, a cyclooxygenase inhibitor, hPGHS-1 produced a narrow singlet but the Y504F mutant did not form a tyrosyl radical. These results indicate that peroxide-induced radicals form on Tyr385 and Tyr504 of hPGHS-1, with radical primarily on Tyr504 in the wild type protein; indomethacin binding prevented radical formation on Tyr385 but allowed radical formation on Tyr504. Thus, hPGHS-1 and -2 have different distributions of peroxide-derived radical between Tyr385 and Tyr504. Y504F mutants in both hPGHS-1 and -2 significantly decreased the cyclooxygenase activation efficiency, indicating that formation of the Tyr504 radical is functionally important for both isoforms.