The bending-rotation spectrum of fulminic acid and deuterofulminic acid

A quasilinear molecular model is needed to account for the infrared absorption spectrum of HCNO and DCNO in the spectral region from 100 cm^?1 to 1000 cm^?1. The observed systems of infrared bands arising from the ν₅ vibrational manifold have all been assigned. The rotational structure of the absorption bands at 225 cm^?1, 275 cm^?1, 315 cm^?1, and 317 cm^?1 for HCNO has been resolved using a Fourier spectrometer. The rotational constants and the band centers have been determined for the above bands, which represent the transitions(0000⁰1¹)_c←0000⁰0⁰(0000⁰2²)_c,d←(0000⁰1¹)_c,dboth components(0000⁰3³)_c,d←(0000⁰2²)_c,d0000⁰2⁰←(0000⁰1¹)_c.By means of the Ritz combination principle the infrared transitions could be used to build up the vibrational energy level scheme of the ν₅ vibrational mode for HCNO and DCNO. The data are only reconcilable with a potential function for ν₅ which exhibits a low barrier opposing linearity. Preliminary values of the potential parameters were obtained using different approximate theoretical approaches.A reinterpretation of the r₈ structure parameters of fulminic acid in the light of the quasilinear model leads to an explanation of the extraordinarily short CH internuclear distance of 1.027 Å as the projection of a CH bond length of 1.060(5) Å upon the heavy-atom axis.The isotopic shift upon deuteration observed in the infrared data indicate that the ν₅ fundamental vibration is primarily an HCN bending motion. The ν₄ fundamental vibration (skeletal bending motion) of HCNO is located at 537 cm^?1 and does not exhibit any hot band structure which would be indicative of a perturbed potential function.     

Impact of different software implementations on the performance of the Maxmin method for diverse subset selection

Besides the choice of an automated software method for selecting 'maximally diverse' compounds from a large pool of molecules, it is the implementation of the algorithm that critically determines the usefulness of the approach. The speed of execution of two implementations of the Maxmin algorithm is compared for the selection of maximally diverse subsets of large compound collections. Different versions of the software are compared using various C compiler options and Java virtual machines. The analysis shows that the Maxmin algorithm can be implemented in both languages yielding sufficient speed of execution. For large compound libraries the Java version outperformes the C version. While the Java version selects the same compounds independent of the virtual machine used, the C version produces slightly different subsets depending on the compiler and on the optimization settings.     

Millimeter-Wave Spectra and Global Torsion-Rotation Analysis for the CH(3)OD Isotopomer of Methanol

New millimeter-wave and microwave measurements for CH(3)OD have been combined with previous literature data and with an extended body of Fourier transform far-infrared observations in a full global analysis of the first two torsional states (v(t) = 0 and 1) of the ground vibrational state. The fitted CH(3)OD data set contained 564 microwave and millimeter-wave lines and 4664 far-infrared lines, representing the most recent available information in the quantum number ranges J 相似文献   

Rotation-torsion-vibration term-value mapping for CH3OH: Torsion-mediated doorways and corridors for intermode population transfer

Fourier transform infrared spectra of CH₃OH from 930-1650 cm⁻¹ have been analyzed to reveal details of the rotation-torsion-vibration energy manifold of the CO-stretching, CH₃-rocking, OH-bending and CH₃-deformation modes and their torsional combination states. Mapping of the upper-state term values as a function of the rotational quantum number J has shown the locations of numerous substate crossing resonances that give rise to J-localized spectral perturbations and substate mixing and thereby create “doorways” for collision-induced population transfer among the different modes. Other near-degenerate substates are more globally mixed over a wide range of J, corresponding to “corridors” of doorways. Where both partner substates in a doorway resonance have been identified, the perturbations have been analyzed to find estimates of the interaction matrix elements and the degree of mixing between the coupled states. Many of the resonances are between substates of differing torsional quantum number, highlighting the importance of torsion in generating the doorway channels and enhancing intermode vibrational population transfer.     

Diode laser spectrum of HCCl near 5 μm: The ν2 fundamental and accompanying hot bands

The CC stretching band ν₂ of iodoacetylene has been studied by tunable laser spectroscopy in the range of 2037–2071 cm^?1. The hot bands associated with the low-lying bending vibrations ν₄ and ν₅ were observed. For the Π-Π hot bands, the splitting caused l-type doubling was resolved for high J transitions. For the fundamental band the hyperfine splittings due to the ¹²⁷I nuclear quadrupole moment were clearly observed for R(0) and P(1) transitions. Combination of these diode laser spectra with the microwave data allows precise determination of the constants in the ground and excited vibrational states.     

The b-type rotational transitions of HNCO in the lowest excited vibrational state

In the microwave and millimeter wave spectra of HNCO, the b-type transitions between the K_a = 0 and 1 levels in the lowest excited vibrational state have been observed. Because of strong a-type Coriolis resonances among the three bending excited states the energy difference between the levels for K_a = 0 and 1 is much smaller in the lowest excited state than in the ground state. The subband origin of these b-type transitions has been found in the millimeter wave region at 275 697.309 MHz (9.1963 cm^?1). The effect of the Coriolis resonances is discussed in relation to the molecular quasi-linearity and is compared with the case of HNCS.     

Simultaneous analysis of the microwave and infrared spectra of 14ND3 and 15ND3 for the ν2 excited state

The data on the inversion spectrum in the ν₂ state of ¹⁴ND₃ [F. Scappini, A. Guarnieri, and G. DiLonardo, J. Mol. Spectrosc.95, 20–29 (1982)] have been extended by measuring frequencies of 25 new transitions. A simultaneous least-squares analysis of these data with the ground state microwave transition frequencies and the diode laser measurements of the ν₂ band has been carried out. Improved sets of molecular parameters have been obtained for ¹⁴ND₃ and ¹⁵ND₃, including the ground and ν₂ state inversion splittings, ν₂ band origins, rotational and centrifugal distortion constants, and the parameters of the Δk = ±3n vibrational-rotational interactions.     

Multidimensional Design of Anticancer Peptides

The computer‐assisted design and optimization of peptides with selective cancer cell killing activity was achieved through merging the features of anticancer peptides, cell‐penetrating peptides, and tumor‐homing peptides. Machine‐learning classifiers identified candidate peptides that possess the predicted properties. Starting from a template amino acid sequence, peptide cytotoxicity against a range of cancer cell lines was systematically optimized while minimizing the effects on primary human endothelial cells. The computer‐generated sequences featured improved cancer‐cell penetration, induced cancer‐cell apoptosis, and were enabled a decrease in the cytotoxic concentration of co‐administered chemotherapeutic agents in vitro. This study demonstrates the potential of multidimensional machine‐learning methods for rapidly obtaining peptides with the desired cellular activities.     

De Novo Fragment Design for Drug Discovery and Chemical Biology

Automated molecular de novo design led to the discovery of an innovative inhibitor of death‐associated protein kinase 3 (DAPK3). An unprecedented crystal structure of the inactive DAPK3 homodimer shows the fragment‐like hit bound to the ATP pocket. Target prediction software based on machine learning models correctly identified additional macromolecular targets of the computationally designed compound and the structurally related marketed drug azosemide. The study validates computational de novo design as a prime method for generating chemical probes and starting points for drug discovery.