Classification of dry-cured hams according to the maturation time using near infrared spectra and artificial neural networks

An attempt to classify dry-cured hams according to the maturation time on the basis of near infrared (NIR) spectra was studied. The study comprised 128 samples of biceps femoris (BF) muscle from dry-cured hams matured for 10 (n=32), 12 (n=32), 14 (n=32) or 16 months (n=32). Samples were minced and scanned in the wavelength range from 400 to 2500 nm using spectrometer NIR System model 6500 (Silver Spring, MD, USA). Spectral data were used for i) splitting of samples into the training and test set using 2D Kohonen artificial neural networks (ANN) and for ii) construction of classification models using counter-propagation ANN (CP-ANN). Different models were tested, and the one selected was based on the lowest percentage of misclassified test samples (external validation). Overall correctness of the classification was 79.7%, which demonstrates practical relevance of using NIR spectroscopy and ANN for dry-cured ham processing control. Key words: dry-cured ham, classification, near infrared spectroscopy, artificial neural network

(Strept)avidin as host for biotinylated coordination complexes: stability, chiral discrimination, and cooperativity

Incorporation of a biotinylated ruthenium tris(bipyridine) [Ru(bpy)₂(Biot-bpy)]²⁺ (1) in either avidin or streptavidin-(strept)avidin-can be conveniently followed by circular dichroism spectroscopy. To determine the stepwise association constants, cooperativity, and chiral discrimination properties, diastereopure (Λ and δ)-1 species were synthesized and incorporated in tetrameric (strept)avidin to afford (δ-[Ru(bpy)₂(Biot-bpy)]²⁺)x⊂avidin, (Λ- [Ru(bpy)₂(Biot-bpy)]²⁺)x⊂avidin, (δ-[Ru(bpy)₂(Biot- bpy)]²⁺)x⊂streptavidin, and (Λ-[Ru(bpy)₂(Biot-bpy)]²⁺) x⊂streptavidin (x = 1-4) For these four systems, the overall stability constants are log β₄ = 28.6, 30.3, 36.2, and 36.4, respectively. Critical analysis of the CD titrations data suggests a strong cooperativity between the first and the second binding event (x = 1, 2) and a pronounced difference in affinity between avidin and streptavidin for the dicationic guest 1 as well as modest enantiodiscrimination properties with avidin as host

Symmetry mapping and recursive reduction of multiplet patterns in nuclear magnetic resonance spectra obtained with two-dimensional correlation and multiple-quantum methods

Chem. shifts and scalar coupling consts. were extd. by symmetry mapping of multiplets in 2-dimensional NMR spectra. The procedure relies on the fact that, in addn. to symmetry with respect to the centers of the multiplets, substructures embedded within the multiplets are partly sym. The recursive anal. is reliable even in the presence of accidental degeneracies, strong coupling, and broad lines as occur in macromols. With minor modifications, the algorithms can be used both for 2D correlation spectra (COSY) and for multiple-quantum spectra, thus allowing complementary evidence to be obtained when accidental overlaps make anal. difficult in either form of 2D NMR spectroscopy. [on SciFinder (R)

Similarities between self-convolution and symmetry mapping of multiplets in two-dimensional NMR spectra

Self-convolution and symmetry mapping were used to analyze proton multiplets in two-dimensional NMR spectra of the triterpene, obtusifolione (I). [on SciFinder (R)

Counter propagation artificial neural networks modeling of an enantioselectivity of artificial metalloenzymes

The counter propagation artificial neural networks (CP-ANNs) were used to develop a quantitative structure-selectivity relationship (QSSR) for a set of artificial metalloenzymes. The artificial metalloenzymes consist of biotinylated rhodium-diphosphine complexes incorporated in streptavidin mutants acting as host protein. Such hybrid catalysts have been shown to be good enantioselective hydrogenation catalysts for acetamidoacrylic acid. The descriptor-based models were constructed to predict enantiomeric excess (%ee) on the basis of the catalyst structures originating from docking simulations. 3D molecular descriptors for the docked ligands structures were computed. The relative arrangement of guest and host molecules was coded using distance descriptors (Rh-Cα interatomic distances); the diversity of the mutant proteins at the position S112 was coded with molecular descriptors for the sequence of three neighboring amino acids (T111-S112X-G113). The selection of testing samples for the external model validation was based on the Kohonen mapping. The final model trained by two thirds of the entire dataset was characterized by satisfactory statistical parameters for the external test set (R = 0.953 and RMS = 16.8 %ee). The proposed procedure of docking-based descriptor generation thus appears as a promising alternative to the full characterization of the complex structure by experimental or computational methods

Double-quantum z-filtered NMR spectra and automated analysis by pattern recognition

A simple variation of double-quantum spectroscopy is described where the transfer of double- into single-quantum coherence is carried out by means of 2 pulses with small flip angles via eigenstate populations and zero-quantum coherences. For systems with 4 or more spins, the sensitivity of the new expt. is comparable to or better than that of conventional double-quantum spectroscopy with a single 90 Deg monitoring pulse. The resulting spectra feature simple 2D multiplets that are composed of juxtapositions of antiphase doublets. The inclusion of pathways involving zero-quantum coherences greatly simplifies exptl. procedures but leads to small deviations from pure 2D absorption peak shapes in systems with 3 or more spins. A simple variation of the technique yields a complementary 2D spectrum which is useful for automated anal. by pattern recognition techniques. Algorithms are described that allow one to det. the topol. of the coupling network and the values of the shifts and coupling consts. The likelihood that a postulated topol. is correct may be detd. from the degree of consistency between expected and exptl. remote multiplets in double-quantum spectra. [on SciFinder (R)