CD3 Groups Research Articles

Vibrationally excited states in C3v molecules: CH and CD stretchings in CH3CD3

Abstract The infrared spectrum of gaseous CH3CH3 has been recorded in the range of 3000–15 000 cm−1. Overtone and combination bands up to five quanta of excitation in CH and CD stretchings have been assigned. A total of 71 vibrational states for CH3, involving stretchings and bendings, has been analyzed on the basis of a normal mode model. The relations between the normal and local mode parameters associated with CH stretchings were imposed and three Fermi resonance interactions were included. Twelve parameters reproduce the experimental data related to CH3 with an r.m.s. error of 2.16. Less satisfactory results have been obtained by treating 36 vibrational states involving stretchings and bendings of the CD3 group with the same model.

Synthesis of (2S,4S)- and (2S,4R)-[5,5,5-2H3] leucine from (R)-pulegone

Beginning with (R)-pulegone, a CD3 group attached to the stereogenic center containing CH3 has been created by conversion to citronellal-1-d, exchange of the acidic hydrogens at C-2 by deuterium, and decarbonylation with Wilkinson's catalyst. Oxidation to isovaleric acid-d3 and conversion to leucine by standard procedures gave the (2S,4S) and (2R,4S) diastereomers (10 and 12) of [5,5,5-2H3]leucine.

Deuterium solid‐state NMR study of the molecular mobility and dehydration of tert‐butyl alcohol on zeolite H‐ZSM‐5

AbstractThe molecular mobility and dehydration reaction of tert‐butyl alcohol, selectively deuteriated in the methyl groups (t‐BuOH[2 – 2H9], dTBA), absorbed on H‐ZSM‐5 zeolite was studied using 2H NMR spectroscopy. At 173–298 K two modes of fast anisotropic motion were observed for the adsorbed alcohol: rotation of CD3 groups around the CC bonds and rotation of the entire (CD3)3C fragment around the CO bond. The influence of the walls of the H‐ZSM‐5 channels on the geometry of adsorbed dTBA is small, the increase in the CD3CO angle not exceeding 2.7 ± 1.2° compared with the same angle in solid dTBA. This is explained by location of the alcohol molecules at channel intersections of the zeolite, whose dimensions exceed those of the dTBA molecule. The lifetime of the dTBA molecule at these adsorption sites exceeds 1 × 10−5 s. The observed reaction products are deuteriated water with an unusual 2H NMR lineshape and two types of butene oligomers: less mobile species with the lineshape typical of solid‐state 2H NMR and more mobile species with a liquid‐like lineshape. The number of more mobile species increases with increase in temperature. In addition, 2H NMR indicates the presence of tert‐butyl groups in the reaction products. For oligomers with a liquid‐like lineshape, the diffusion coefficient D is 3 × 10−13 m2 s−1 at 373 K, whereas for oligomers with a solid‐like lineshape D ≪ 5 × 10−14 m2 s−1 at 173‐373 K. The diffusion coefficient for the t‐BuOH molecule was estimated as D ≪ 2 × 10−14 m2 s−1 within the temperature range 173–296 K.

Symmetry-species conversion in CD3 systems

The rates for symmetry-species conversion of CD3 groups are calculated using a model in which the interaction between the quadrupolar moment of the deuterons with electric-field gradient at the site of the nucleus causes symmetry-changing transitions. Just the same phonons are considered for energy conservation as are used to describe the temperature dependence of inelastic neutron scattering experiments. For the conversion rate, a similar temperature dependence is found as has already been obtained for CH3. For temperatures around the tunnelling energy, a behaviour is predicted for CD3 that is different from the behaviour in protonated systems according to all theories known to the authors. In comparison with the corresponding protonated species embedded in the same surroundings, the conversion rate at elevated temperatures turns out to be larger by orders of magnitude. Only the low-temperature conversion rate is suppressed owing to the lack of resonance phonons at the usually smaller tunnelling frequency in CD3. The relative increase of the conversion rate with deuteration due to Raman processes is predicted to be independent of temperature but strongly dependent on the height of the orientational potential in the case of shallow potentials. If the tunnelling energy is smaller than 25 mu eV, the conversion rates increase by a constant factor of approximately 10 compared to the protonated species at a given temperature.

The Millimeter-Wave Spectrum of Dimethylether-D 6 in Excited Torsional States

The rotational spectrum of dimethylether-D 6 in the first two excited torsional states between 40 and 100 GHz has been measured, and the rotational and quartic distortion Constants for both states are given. The analysis of the internal rotation gives the potential parameters V 3 and V′ 12 and the angles between the principal axes of inertia and the internal rotation axes. Also, the moment of inertia I α of the CD 3-group has been determined.

Probing the early stages of polymerization of ethylene on a model chromium/silica catalyst by Fourier transform infrared spectroscopy

The nature of the interaction of monomer, and the early stages of growth of oligomers of ethylene on a rather more uniform surface of Cr/SiO2 catalyst than hitherto studied has been investigated by differenceFTIR spectroscopy using C2D4 and C2H4 as reactants both with and without subsequent treatment of the catalyst with CO andTHF. The active catalyst was prepared by reaction of vapour phase CrO2Cl2 with the vicinal hydroxyls of the silica surface. Three distinct kinds of methylene groups were detected. Arguments are given for assigning the peaks at 2935 and 2860 cm−1 to CH2 groups directly bound to the active site and those at 2920 and 2850 to CH2s in the growing chain well removed from the Cr. The peaks at 2160 and 2165 cm−1 are attributed to CD2 groups hydrogen bonded to surface hydroxyls.

(13C,2H) residual dipolar and indirect spin–spin coupling effects in high-resolution13C nuclear magnetic resonance spectra of solids

We report high-resolution solid-state 13C NMR spectra of urea and thiourea inclusion compounds containing deuteriated guest molecules. The spectra (recorded under conditions of magic-angle sample spinning and high-power 1H decoupling at several magnetic fields from 4.7 to 11.7 T) for CD, CD2 and CD3 groups are triplets, pentets and heptets, respectively. These multiplets arise from the effects of residual dipolar interaction and indirect spin–spin coupling between 13C and 2H. A full analysis of these lineshapes is presented, and the effect of molecular motion is discussed. It is shown that the 13C NMR lineshape for deuteriated materials which are in a rapid motion regime (with respect to the 2H NMR timescale) can be rationalized by considering the motionally averaged 2H quadrupole coupling constant 〈χ〉.

Proton NMR detection of cationic organopalladium(IV) intermediates in oxidative-addition reactions and the structure of fac-PdBrMe2(CH2COPh)(bpy)

Phenacyl bromides react with dimethylpalladium(I1) complexes PdMe2(L2) (L2 = bpy, phen) to form the palladium(IV) complexes fac-PdBrMe2(CH2COAr)(L2) (Ar = Ph, p-C6H4Br), which have both methyl groups trans to the bidentate nitrogen donor ligand. 1H NMR studies of the oxidative addition of phenacyl bromides to PdMe2(bpy) in (CD3)2C0 at -5 C indicate the formation of two similar cationic intermediates, prior to formation of the neutral product. As the cations have only one of the methyl groups trans to bpy, configurational changes at palladium occur on cation formation and on conversion of the cations to the neutral product. It is proposed that one of the cations may be stabilized via an intramolecularly coordinated phenacyl group, [PdMe2(CH2COAr-C,0)(L2)]+. A single cation, exhibiting NMR spectra similar to those of the cations of the bpy complexes, is detected as an intermediate in the reaction of PdMe2(phen) with ArCOCH2Br. A cation has also been detected for the reaction of PdMe2(bpy) with CD3I in (CD3)2C0 at -50 C, prior to formation of PdIMe2(CD3)(bpy). Both the cation, most likely [PdMe2(CD3)(bpy)((CD3)2CO)]+, and the neutral product display scrambled Me and CD3 groups, in contrast to the trans oxidative addition reported for the analogous reaction of PtMe2(bpy) with CD3I. Crystals of PdBrMe2(CH2COAr)(bpy) are orthorhombic, space group Pbca, with a = 19.554(3) A, b = 15.007(9) A, c = 13.282(4) 1, and Z = 8.

Quantum mechanical behaviour of deuterated methyl groups

We discuss the temperature dependence of deuterium NMR spectra and spin-lattice relaxation rates 1/T 1 of deuterated methyl groups. We restrict ourselves to the temperature range where it is sufficient to consider only the two lowest librational levels of the CD3 group. Specifically we derive explicit expressions for 1/T 1 and the widthГ NMR of the so-called tunneling resonances in the high-field NMR spectrum in the limit where the tunneling frequencyΔ 0 is large compared to the quadrupole coupling constant of a methyl group. We demonstrate that the disappearance of the tunneling resonances at elevated temperatures follows the scenario of the NMR of nuclei which exchange classically between two inequivalent sites. We further show that the NMR linewidths and relaxation rates are strongly related to the widths of the quasielastic and inelastic lines in incoherent neutron spectra. It turns out that for NMR spectra the classical limit is usually reached at lower temperatures than for neutron spectra. All calculations are based on the projection operator formalism.

E.S.R. Spectra of Free Radicals Relevant to Methacrylate Polymerization

Carbon-based free radicals were generated by thermal cleavage of the tetraester Me2C(COOME)-CH2-CMe( COOMe )- CMe ( COOMe )-CH2-C( COOMe )Me2 which is a model for head-to-head units in a poly(methyl methacrylate ) chain. The resulting electron spin resonance spectrum had higher resolution than the 'nine-line' spectrum previously reported; this enabled identification of the component radicals. In the present case, the spectrum was well matched by a summation of spectra of the Me2C(COOME)-CH2-CMe( COOMe ) radical and the 1-methoxycarbonyl-1-methylethyl radical Me2-C-COOMe derived from it by loss of methyl methacrylate. Both of these radicals were generated in separate experiments. Radicals were also generated from starting materials containing a CD3 group in place of the single CH3.

Coenzyme F430 from Methanogenic Bacteria: Detection of a Paramagnetic Methylnickel(II) Derivative of the Pentamethyl Ester by 2H‐NMR Spectroscopy

AbstractA methylnickel(II) derivative of coenzyme F430 (1) was proposed as an intermediate in the enzymic process catalyzed by methyl‐CoM reductasc. Indirect evidence points to formation of CH3–F430MII in the reaction of F30M1 (obtained from F430MII (2)) with eleclrophilic methyl donors. The results presented here show, that such a compound does exist. A paramagnetic CD3–NiII derivative 5b of the pentamethyl ester 2 (F430M) of coenzyme F430 was prepared by in situ methylation with (CD3)2Mg and characterized by its isotropically shifted 2H‐NMR spectrum. At −40°, the very broad D‐signal of the axially coordinated CD3 group is found at −490 ppm. Comparison with the 2H‐ and 1H‐NMR spectra of mcthyl(tetramethylcyclam)nickel(II) derivatives 4 ([NiII(CH3))(tmc)]CF3SO3 (4a) is the only isolated CH3–Ni derivative of a N4macrocyclic NiII complex' shows that the large isotropic shift to high field is characteristic for a Me group axially bound to the Ni center. The temperature dependence of the isotropic shift of the CD3–Ni group in both 4b and 5b follows Curie's law and yields 2H hyperfine coupling constants of −0.65 (4b) and −0.85 MHz (5b), respectively. The 1H‐NMR spectrum indicates that, in contrast to the five‐coordinate monochloro complex [NiIICl(tmc)]+, intermolecular exchange of the axial ligand in [NiII(CH3)(tmc)]+ 4a is either slow at the NMR time scale or does not occur at all.

Antibodies to different members of the β1 (CD29) integrins induce homotypic and heterotypic cellular aggregation

Members of the β 1 (CD29) integrin family are involved in cellular adhesion to extracellular matrix. However, there have been several reports of CD29 integrin participation in intercellular adhesion. For example, the treatment of the human T cell line Jurkat with antibodies to α 4 (CD49d) causes homotypic aggregation. The present report describes the induction of aggregation of Jurkat cells by antibodies to α 5 (CD49e) and to a lesser extent by antibodies to the common β 1 CD29 chain of these integrins. The metabolic requirements for these aggregations are compared with that of the CD49d-induced process. The possible involvement of fibronectin in the cytoadhesion appears to be unlikely as (1) the aggregates form in the absence of plasma fibronectin; (2) antibodies to fibronectin do not inhibit the cell adhesion; and (3) exogenous fibronectin does not influence the process. One of the cognate partners involved in the CD49e-induced aggregation appears to be present on non-antibody-treated Jurkat cells as the cells are coincorporated into aggregates of anti-CD49e-stimulated cells. The adhesion does not appear to involve members of the CD2, CD3, CD4, or CD18 receptor groups. These results indicate that interaction with α 4, α 5 chain or the β 1, chain of the CD29 integrins leads to the induction of intercellular adhesion. The possible biological significance of this process is discussed.

CD2 rocking modes as quantitative infrared probes of one-, two-, and three-bond conformational disorder in dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylcholine/cholesterol mixtures

The use of CD2 rocking modes in the IR spectrum as quantitative probes of phospholipid conformational disorder has recently been described for aqueous dispersions of 1,2-dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol mixtures [Mendelsohn et al. (1989) Biochemistry 28, 8934-8939; Davies et al. (1990) Biochemistry 29, 4368-4373]. Initial studies focused at the 4, 6, and 10 acyl chain positions of DPPC. In the current work, the method is extended to the 2, 3, 12, and 13 positions. Conformational disorder in the L alpha phase is approximately the same (about 20% gauche) at positions 4, 10, and 13, but an unexpected higher value is observed (about 30%) at the 6 position. Cholesterol (33 mol%) restricts gauche rotamer formation by factors ranging from 6 to 9 at positions 4 and 6, respectively, to 1.5-2 at positions 10, 12, and 13. Quantitative analysis for the DPPC/cholesterol "liquid-ordered" phase indicates the occurrence of 1.2 gauche bonds/chain, a marked reduction from the 3.6-4.2 gauche bonds/chain for DPPC alone. Proximity to the ester moiety at acyl chain position 3 perturbs the vibrational coupling patterns of the CD2 rocking modes and eliminates their sensitivity to conformational change. In addition, the feasibility of a method based on the conformation-dependent coupling between CD2 rocking frequencies of two successive CD2 groups for the quantitative detection of specific, position-dependent king (gtg') and isolated gauche (gtt) conformers is demonstrated. Finally, comparisons between IR measurements and explicit theoretical predictions of acyl chain conformational order are presented.

The configuration and the dynamics of the -CD3groups in methyl deuterated dimethylmalonic acid

The angular variation of the deuteron NMR of single crystals of methyl deuterated dimethylmalonic acid, C(CD3)2(COOH)2 (DMMA), was measured at room temperature and at 56 K. From the room temperature data the motionally averaged deuteron quadrupole coupling tensors for rapidly reorienting methyl groups are determined. The C-Cmethyl bond directions are inferred from the unique principal axes of these tensors. A semi-quantitative analysis of the 56 K data leads to the conclusion that at this temperature the methyl groups are immobile and that the configuration of the two methyl groups within the DMMA molecule is an eclipsed one. By line shape analysis of deuteron spectra recorded for 290 K > T > 60 K the Arrhenius parameters for reorienting -CD3 groups E a = 9·5 kJ mol-1 and k (D) 0 = 0·8 × 1011 s-1 were determined. No features giving evidence for tunnelling could be observed in the low temperature deuteron spectra. An upper limit of 3 kHz is derived for the -CD3 tunnel frequency v (D) t for T → 0.

Spin lattice relaxation rates of tunnelling CD3 groups

The spin lattice relaxation rates of deuterated methyl groups are calculated for threefold and sixfold potentials. It is shown that it should be possible to determine the symmetry of the potential hindering the methyl groups from deuteron spin lattice relaxation experiments. The temperature dependence of the spin lattice relaxation rates is discussed using a simple model. The similarities and the differences between proton NMR and deuteron NMR are pointed out. The main difference is thatEa↔Eb transitions are forbidden by spin selection rules in case of CH3, but not for CD3. Therefore, and due to the fact that the quadrupolar interaction is a single particle interaction, deuteron NMR allows the study of the rotational dynamics of single methyl groups.

Calculation of anharmonic force constants for the CD3 group from the Raman spectra of (CD3)(CH3)3NI

The anharmonic force constants for the CD 3 group, W 12 (k 122 ), W 13 (k 133 ) and W 23 (k 2233 ), were calculated by a method in which the only approximation is the neglect of the intrinsic intensities of the unperturbed transitions 2δ g o and 2δ a o . Using Raman data for (CD 3 )(CH 3 ) 3 NI solutions, the calculated values of the anharmonic forces constants are W 12 =42.5 cm −1 , W 13 =21.5 cm −1 and W 23 =9.4 cm −1

Long‐range deuterium isotope effects in tautomeric β‐thioxoketones. A 1H and 13C NMR study

AbstractEquilibrium displacements within the enol–enthiolic tautomeric systems of β‐thioxoketones caused by long‐range isotope effects were monitored by 1H and 13C NMR spectroscopy. Thioacetylacetone and 1,3‐diphenyl–3‐thioxopropanone deuteriated at various positions were investigated. Both compounds are in fast (Z)‐enol‐(Z)‐enethiol equilibrium on the NMR time scale. The investigations showed that CD3 and C6D5 groups changes the equilibrium so that the tautomer having a C  X bond next to the CD3 or C6D5 groups decreases. Deuteriation at the methine position pushes the equilibrium towards the (Z)‐enol form. The study further showed that deuteriation at the phenyl ring next to the C  O group causes the largest effect if the deuterium is at the ortho position and the smallest if it is at the para position. Long‐range effects on equilibrium are discussed in general in order to establish a common pattern. Deuterium scrambling is observed both during the coupling reaction of ethyl thionoacetate with hexadeuterioacetone and during preparation of specifically labelled acetophenone. The latter compounds are synthesized by acetylation of specifically labelled benzenes. The scrambling reaction is suggested to be a transdeuteriation of the deuteriated benzenes rather than involving the acetophenones.

Inter- and intramolecular interactions and rotational tunneling of methyl groups in tetramethyltin

Rotational tunneling of methyl groups in partially deuterated tetramethyltin compounds, (CH3)xSn(CD3)4−x with x=1 and 3, and in various isotopic mixtures, [(CH3)4Sn]x[Sn(CD3)4]1−x, x=0.027, 0.20, and 0.50, and [CH3Sn(CD3)3]x[Sn(CD3)4]1−x, x=0.10, respectively, has been studied using the inelastic neutron-scattering (INS) technique. Compared with the INS spectrum of fully protonated tetramethyltin, (CH3)4Sn, the spectra obtained in the present study show remarkable shifts and broadenings or splittings of tunnel lines. The interpretation of the INS results is based on the assumption that all partially deuterated compounds and isotopically mixed systems have the same crystal structure as pure (CH3)4Sn. Combining the INS results with a detailed discussion of the crystal structure, all features can be explained in terms of both the intra- and intermolecular interactions of methyl groups. The overall decrease of tunnel splittings with deuteration is explained by the reduction of the lattice parameter and the increased octopole moment of the CD3 groups. The interaction between different molecules is mediated by a subset of methyl group pairs only.

The impact of age on T cell subset profiles in patients on chronic hemodialysis awaiting renal transplantation

Age has been considered a significant risk factor in renal transplation; increasing age is associated with a higher morbidity and mortality, primarily as a consequence of infectious and cardiovascular complications. The increased incidence of potentially lethal infections in this patient population may be due to the impact of immunosuppression on a naturally declining immune system. In search for possible characteristic T cell subsets profile in aging patients, subsets of such cells were analyzed in 270 patients on chronic hemodialysis awaiting renal transplantation. Using two-color flow cytometry and murine monoclonal antibodies recognizing specific T cell subset markers, the following cell subsets were analyzed in patients 55 (n = 41) years of age: total T cells (CD3); activated T cells (CD3DR); B cells (CD3-DR+); T helper/inducer (h/i) cells (CD4); T suppressor/inducer (s/i) cells (CD4+CD45+), T cytotoxic/suppressor (CD8), the activated CD4 and CD8 subsets (CD4DR and CD8DR); T cytotoxic cells (Leu2+7−); cells of the Leu-7 phenotype (Leu7+ and Leu2+7+); interleukin 2 receptor (IL-2-R) expressing CD3 and CD8 subsets (CD3IL-2−R+ and CD81L2-R+); and transferrin receptor (TR+) expressing CD3 (CD3TR+). The ratio CD4: CD8 was derived from the respective subset data. Significantly higher levels of CD3 (P 55) group. In contrast, the CD4 : CD8 ratio, the s/i (CD4+CD45+), the Leu7+2- and Leu2+7+ cell subsets were found to be present at a higher level in the older group (P < 0.001, P < 0.005, P < 0.05 and P < 0.01 respectively). These data demonstrate a significant effect of aging on certain T cell subsets levels in the peripheral blood. Although this study does not provide data regarding the functional status of the immune competent cells, it highlights the actual changes in the distribution of cell subsets in the older potential organ recipients. Such changes may be responsible for the increased risk of infectious complications seen in older renal allograft recipients.

2H/1H Isotope Shifts for 6Li‐NMR: First Experimental Detection and Applications to Structural Problems in the Field of Organolithium Compounds

AbstractDeuterium‐induced isotope effects on 6Li chemical shifts, transmitted over two bonds, 2Δ(6Li)(2H/1H), have been measured for the first time for methyllithium and the system methyllithium/lithium iodide. The observed shifts are to low field and range from 15 to 20 ppb per CD3 group. The multiplicity and intensity distribution of the 6Li signals resulting for mixtures of CH3‐ and CD3‐containing samples in the limit of slow inter‐ as well as intra‐aggregate exchange yield information about the size of the various clusters present in diethylether solution. It is expected that these isotope shifts can facilitate structural investigations of organolithium compounds. In some cases, the results of such measurements are expected to be less ambiguous then the conclusions based on multiplets that arise from scalar 13C,6Li spin‐spin coupling.