Heterodyne laser spectroscopy of lithium ions: 23 P fine and hyperfine structure of7Li+

The fine structure (fs) splittings in the 1s2p ³ P _J=1,2,0 multiplet of the helium-like⁷Li⁺ ion were measured with a laser spectrometer. The results with 3σ errors are: Δv ₀₁ (³ P ₀,F=3/2?³ P ₁,F=5/2)=152081.6(2.0) MHz and Δv ₀₂ (³ P ₀,F=3/2?³ P ₂,F=7/2)=82704.3(1.9) MHz. Combining the new precise fs measurements with earlier hyperfine structure (hfs) results from laser-microwave spectroscopy provided improved fs constants:D ₁=?155709.0(2.1) MHz,D ₂=?93049.2(2.0) MHz, and hfs constants:A _c =3679.0(6) MHz,A ₀=51.0(4) MHz, andA _d =?11.3(1) MHz, thus allowing for a stringent test of available theoretical data. The spectroscopic method used in this work opens up the possibility of determining Li⁺, 2³ S?2³ P absolute transition frequencies with a precision of ～2·10^?9.     

Synthesis and properties of homomologated and contracted dipyrrinone analogs of xanthobilirubic acid

Dipyrrinone analogs of xanthobilirubic acid, 5-[1,5-didehydro-3-ethyl-4-methyl-5-oxo-2H-pyrrol-2-ylidene)-methyl]-2,4-dimethyl-1H-pyrrol-3-propanoic acid, with alkanoic acid chain lengths varying from formic to caproic have been synthesized as their methyl esters and characterized spectroscopically. All of the dipyrrinones studied exhibit intermolecular hydrogen bonding in chloroform, as detected by ¹H-nmr, and the influence of the carboxyl group on the uv-visible spectrum decreases with increasing chain length.     

Design of unusual captodative methylene substrates: 1-Alkyl-4(3)-(azolylmethyl)pyridinium salts 1

The unprecedented spontaneous oxidation of a carbon atom linked to captor (acceptor) and donor non-classical functional groups of several examples of 1-alkyl-4(3)-(1H-azolylmethyl) pyridinium salts 1 and 2 exemplifies a concomitant application of the arenoanalogy principle and the captodative effect in organic synthesis. A remarkably driving force by the nature of non-classical acceptor and donor heteroaromatic rings is observed upon the chemical behavior of the title compounds 1 and 2, modulating the susceptibility with which the methylene spacers oxidize to their oxomethyl counterparts 5 and 6. Access to dipolar 1-alkyl-3-pyridiniomethyl-3(5)-1,2,4-triazolate inner salts 4 was achieved.     

Oxazepines and thiazepines. XIX Synthesis of optically active 2,3-dihydro-1,5-benzothiazepin-4(5H)-ones

Optically active 2,3-dihydro-1,5-benzothiazepin-4(5H)-ones (14–17) have been synthesizedvia resolution and chemical transformation of nitrocarboxylic acids6–9. Starting from the latter various optically active substances have been synthesized as well. Optical purity was checked by NMR spectroscopy.Dedicated to Prof. Dr.G. Snatzke on the occasion of his 60th birthday.     

X-ray, 31P CP/MAS,and single-crystal NMR studies,and 31P DFT GIAO calculations of inclusion complexes of bis[6-O,6-O'-(1,2:3,4- diisopropylidene-alpha-D-galactopyranosyl)thiophosphoryl] disulfide: the importance of C-H...S=P contacts in the solid state

Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl) thiophosphoryl] disulfide shows a strong tendency to form inclusion compounds. The crystal and molecular structure of eight different solvates was established by X-ray analysis. The results indicate three different types of disulfide arrangements in the crystal lattice. By means of 31P CP/MAS NMR experiments the principal values delta 11, delta 22, and delta 33 of the 31P chemical shift tensor were obtained for each form. The orientation of its principal axes with respect to a molecular frame was investigated by means of 31P CP and single-crystal NMR for the complex with propan-2-ol. The principal axis 1 of both chemically equivalent phosphorus atoms is nearly parallel to the P-S bond and the principal axis 3 is very close to the P=S bond. DFT GIAO calculations of the model compound (EtO)2(S)P1SSP2(S)-(OEt)2 allowed assignment of the experimental chemical shift curves to the magnetically nonequivalent atoms P1 and P2. The maximum difference between calculated angles [symbol: see text] i-P-X)calcd and experimental angles [symbol: see text] i-P-X)exptl is 8.3 degrees and the rms distance 3.8 degrees (i = principal axes 1, 2, 3; X = S, -S-, -O1-, -O2-). The influence of C-H...S weak hydrogen bonding on phosphorus shielding was tested theoretically (31P DFT GIAO) employing the dimethoxythiophosphoryl disulfide.CH4 complex as a model compound. The sensitivity of 31P delta ii parameters to intermolecular forces is demonstrated.     

Simulated Molecular Evolution for Anticancer Peptide Design

A computational technique based on a simulated molecular evolution protocol was employed for anticancer peptide (ACP) design. Starting from known ACPs, innovative bioactive peptides were automatically generated in computer‐assisted design–synthesize–test cycles. This design algorithm offers a viable strategy for the generation of novel peptide sequences, without requiring a priori structure–activity knowledge. Sequence morphing and activity improvement were achieved through iterative amino acid variation and selection. Results show that not only the interaction of ACPs with the target membrane is important for their anticancer activity, but also the degree of peptide dimerization, which was corroborated by temperature profiling and electrospray mass spectrometry.     

Identification of Chemokine Ligands by Biochemical Fragmentation and Simulated Peptide Evolution

Short linear peptides can overcome certain limitations of small molecules for targeting protein–protein interactions (PPIs). Herein, the interaction between the human chemokine CCL19 with chemokine receptor CCR7 was investigated to obtain receptor‐derived CCL19‐binding peptides. After identifying a linear binding site of CCR7, five hexapeptides binding to CCL19 in the low micromolar to nanomolar range were designed, guided by pharmacophore and lipophilicity screening of computationally generated peptide libraries. The results corroborate the applicability of the computational approach and the chosen selection criteria to obtain short linear peptides mimicking a protein–protein interaction site.     

Effect of colour centres (F′-centres) on the depolarization of positive mouns in KCl

The Korringa-Kohn-Rostoker-coherent-potential-approximation (KKR-CPA) method for treating electronic states in random alloys has been made charge self-consistent. Results are presented for a Ag_0.2Pd_0.8 alloy that were obtained using the Hedin-Lundqvist local density exchange-correlation potential.     

Nuclear quadrupole moments of radioactive83Rb,84Rb and86Rb

Excited atomic² P _3/2-states of radioactive Rb isotopes have been investigated by level crossing and optical double resonance spectroscopy. The measured hyperfine structure constants yielded the nuclear moments $$\begin{gathered} \mu _I (^{84} Rb) = - 1.296(11)\mu _K Q(^{83} Rb) = + 0.27(5) \cdot 10^{ - 24} cm^2 \hfill \\ Q(^{84} Rb) = + 0.005(13) \cdot 10^{ - 24} cm^2 \hfill \\ Q(^{86} Rb) = + 0.20(3) \cdot 10^{ - 24} cm^2 \hfill \\ \end{gathered} $$ and the hyperfine anomaly₈₄Δ₈₅=+1.7(1.0) · 10^?2. The quadrupole moments of⁸³Rb to⁸⁷Rb can be explained with the unified model of vibrations.