Monitoring of yeast fermentation by ion mobility spectrometry measurement and data visualisation with Self-Organizing Maps

Ion mobility spectrometry (IMS) measurement combined with unsupervised neurocomputing is considered as a new potential method for on-line monitoring of fermentation and other processes producing volatile compounds that involve micro-organisms. This was demonstrated in a model system in which a strain of brewer’s yeast (Saccharomyces cerevisiae) was cultivated in a bench-top fermenter. Five phases of yeast growth could be detected from measurements of the exhaust gases from the fermenter, as indicated by the changes in ion mobility spectra analysed by computational methods.The data were first processed using the Self-Organizing Map (SOM) algorithm, the results showing that the phases of fermentation can be detected and identified. The cultivations were also shown by Sammon’s mapping to be comparable to a certain level of accuracy. Contaminated cultivation could be detected by its distinctive ion mobility spectrometry profile.     

Simulation of13C NMR chemical shifts for polychlorinated and polybrominated oxybenzenes with two-particle increment scheme

A two-particle system of OY-Cl and OY-Br mixed increments for predicting¹³C NMR chemical shifts of polyhalogenated polyoxybenzenes has been developed. It has been found that only theortho- and para-interactions of the OY and Hal substituents contribute significantly to the¹³C chemical shifts and that theortho-effects of the OY located between Ha1 and H and those of the OY located between two Ha1 atoms are different. Additional effects are due to solvating solvents. The increment scheme is predictive over the whole class of compounds under consideration and may be realized on personal computers.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 617–624, April, 1994.     

Reaction of ruthenium carbonylcarbide cluster Ru6C(CO)17 with nickelocene and pentamethylcyclopentadiene

The reaction of cluster Ru₆C(CO)₁₇ (1) with nickelocene is studied. Five CO ligands rather than a metal-ligand crown are substituted for two cyclopentadienyl groups to give a new complex Ru₆C(⁵-Cp)₂(CO)₁₂ (2). The reaction of cluster1 with entamethylcyclopentadiene leads to new complex Ru₆C(-¹⁵-CH₂C₅Me₄)(CO)₁₄ (3) containing the cr-bond CH₂-Ru, along with an ⁵-coordinated cyclopentadienyl ring.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1171–1172, June, 1995.     

The temperature-dependent red-shift of the visible absorption spectra of crystal violet in alcohol solutions

The visible absorption spectrum of the triphenylmethane dye, crystal violet, in various alcohol solutions at several temperatures has been recorded and subsequently analyzed by computer fitting. The observed spectral changes do not sustain either the earlier temperature-dependent absorption results of Lewis and co-workers or the concept of two ground-state species in equilibrium.     

Metal clusters on an inert surface: a simple model

The shapes of metal clusters (with 2 to 14 valence electrons) on an inert surface are studied with a simple model based on the ultimate jellium model. It is shown that within certain approximations the surface-cluster interaction can be described with an external potential in the Kohn-Sham method. No restrictions for the cluster geometry are imposed. The results show that depending on the strength of the interaction and on the size of the cluster, the ground state is either planar or three-dimensional, but in many cases both geometries are stable and there is a marked energy barrier between them. The results agree qualitatively with ab initio calculations of Na clusters on a NaCl(100) surface.     

H, C NMR spectral and single crystal structural studies of toxaphene congeners. Quantum chemical calculations for preferred conformers of 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene and their DFT/GIAO C chemical shifts

The ¹H and ¹³C NMR chemical shifts for six toxaphene congeners: 2-exo,3-endo,6-exo,8,9,10-hexachloro- (1), 2-exo,3-endo,5-exo,9,9,10,10-heptachloro- (2), 2-exo,3-endo,6-exo,8,9,10,10-heptachloro- (3), 2-exo,3-endo,5-exo,6-endo,8,9,10-heptachloro- (4), 2-exo,3-endo,5-exo,6-endo,8,9,9,10-octachlorobornane (5) and 2,5-endo,6-exo,8,9,9,10,10-octachloro-2-bornene (6) are reported. Their chemical shift assignments have been obtained by means of Pulsed Field Gradient (PFG) Double Quantum Filtered (DQF) ¹H,¹H correlation spectroscopy (COSY), PFG ¹H,¹³C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG ¹H,¹³C Heteronuclear Multiple Bond Correlation (HMBC) experiments. A single crystal X-ray structural analysis was made for compounds 1, 3, 4 and 6. The prevalences of two octachlorobornene rotamers (6a,6b) were elucidated by ab initio MO method and single point DFT/GIAO calculations for ¹³C chemical shifts. Theoretical calculations proved that the single crystal structure of 6 corresponds its most stable conformer in solution.     

The identification of vicinally substituted cyclohexane isomers in their mixtures by 1H and 13C NMR spectroscopy

The radical addition reactions of organobromine compounds, XBr (X = CH2COOMe, PhCH2, CHBr2 and CCl3) with cyclohexene afforded mixtures of cis/trans isomer pairs of 1-X-2-Br-cyclohexanes. In addition to benzyl benzoyloxy derivatives are formed also, when benzoyl peroxide is used as an initiator. Owing to the great difficulties in separating these cis/trans isomer pairs, they are identified directly in their mixtures by NMR spectroscopy. In addition to one-dimensional (ID) 1H, proton decoupled 13C and DEPT-135, also two-dimensional (2D) 13C-13C INADEQUATE as well as 1H-13C HMQC experiments have been used in assigning the signals of each compound in their mixtures. The identification of each isomer was based on comparison of experimental 3J(H,H) coupling constants with theoretical ones based on the well-known Karplus type relationship. The more stable conformation for each isomer was estimated using the semiempirical AM1 molecular orbital method. The calculations support the isomer pair elucidations.     

H, C, N NMR, ESI mass spectral and single crystal X-ray structural characterization of three spiro[pyrrolidine-2,3′-oxindoles]

Three spiro[pyrrolidine-2,3′-oxindoles], 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-phenyl-spiro[3H-indole-3,3′-[3H]-pyrrolizine]-2′-carboxylic acid methyl ester (1), 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-phenyl-spiro[3H-indole-3, 3′-[3H]-pyrrolizine] (2) and 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-(4″-chlorophenyl)-spiro[3H-indole-3,3′-[3H]-pyrrolizine] (3) have been synthesized and their ¹H, ¹³C and ¹⁵N spectra assigned. The chemical shift assignments are based on Pulsed Field Gradient (PFG) Double Quantum Filter (DQF) ¹H, ¹H correlation spectroscopy (COSY), PFG ¹H, ¹³C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG ¹H,X (X = ¹³C and ¹⁵N) Heteronuclear Multiple Bond Correlation (HMBC) experiments. The single crystal X-ray structures of 1–3 have been determined. Compounds 1 and 2 crystallized in monoclinic space group C2/c and compound 3 in monoclinic space group P2₁/c, respectively. Also the ESI-TOF MS data of 1–3 are given.     

A multinuclear 1H, 13C, and 15N magnetic resonance study of ten 4-nitropyridine N-oxides

The ¹H, ¹³C, and ¹⁵N NMR chemical shifts of ten 4-nitropyridine N-oxide derivatives are assigned. The shielding of the pyridine ring nitrogen is sensitive to ring substitution through inductive effects, steric effects by ortho-substituents, and the possibility for electron delocalisation (resonance energy). In solution, 3-ethylnitrosoamino-4-nitropyridine N-oxide has two tautomers. The proposed reason is the steric crowding between vicinal 4-nitro and 3-ethylnitrosoamino groups, causing a disturbance to amino nitrogen that can delocalize its lone pair to the oxygen atom of the nitroso group.     

Surface and curvature properties of neutron-rich nuclei

We use the extended Thomas-Fermi approximation and Skyrme-type interactions to describe the energy density of a semi-infinite slab of neutron-rich nuclear matter at zero temperature. We allow for the existence of a drip phase at low proton fractions in addition to the more dense nuclear phase. We determine various bulk properties of both phases when the system is in equilibrium. We extend the usual definition of the surface energy to apply to the case where drip is present. Assuming the density profile has the form of a Fermi function to a power, we perform a constrained variational calculation to determine the parameters of the density profile. The surface and curvature energies are calculated for proton fractions ranging from 0.5 (symmetric nuclear matter) to 0 (pure neutron matter) for typical Skyrme-type interactions. We find significantly different asymmetry dependences for different interactions. For proton fractions close to 0.5, our results are in close agreement with the predictions of the droplet model. We also present results of calculations for fission barrier properties and phase transitions between nuclei and bubbles to highlight the role of surface and curvature energies in the neutron-rich regime.