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https://www.readbyqxmd.com/read/28079923/vibrational-circular-dichroism-of-a-2-5-diketopiperazine-dkp-peptide-evidence-for-dimer-formation-in-cyclo-ll-or-ld-diphenylalanine-in-the-solid-state
#1
Ariel Pérez-Mellor, Anne Zehnacker
The diastereomer diketopiperazine (DKP) peptides built on phenylalanine, namely, cyclo diphenylalanine LPhe-LPhe and LPhe-DPhe, were studied in the solid phase by vibrational circular dichroism (VCD) coupled to quantum chemical calculations. The unit structure of cyclo LPhe-LPhe in KBr pellets is a dimer bridged by two strong NH…O hydrogen bonds. The intense bisignate signature in the CO stretch region is interpreted in terms of two contributions arising from the free COs of the dimer and the antisymmetrical combination of the bound COs...
January 12, 2017: Chirality
https://www.readbyqxmd.com/read/28078764/photoisomerization-of-a-chiral-imine-molecular-switch-followed-by-matrix-isolation-vcd-spectroscopy
#2
Corina H Pollok, Tim Riesebeck, Christian Merten
Characterizing the stereochemistry of transient photoisomerization products remains a big challenge for the design of molecular machines, such as unidirectional molecular motors. Often these states are not stable long enough to be characterized in detail using conventional spectroscopic tools. The structurally simple camphorquinone imine 1 serves to illustrate the advantage of combining the matrix-isolation technique with vibrational circular dichroism (VCD) spectroscopy for the investigation of photoisomerizations of chiral molecules...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28070081/structural-discrimination-between-a%C3%AE-1-40-and-a%C3%AE-1-42-peptides-in-films-with-vibrational-circular-dichroism-spectroscopy
#3
Toshinori Morisaku, Hiroharu Yui
The secondary structure of full-length Aβ(1-40) and Aβ(1-42) peptides in films has been investigated with IR and vibrational circular dichroism (VCD) spectroscopy. From IR spectra, it is shown that the prepared films of Aβ(1-40) and Aβ(1-42) mainly comprise the β-sheet conformation that is characteristic of aggregated and fibrous Aβ. In the VCD spectra, the Aβ(1-42) film shows an intense and sharp band with left-handed optical activity at around 1625 cm(-1), while the Aβ(1-40) film shows a weak and broad band with right-handed activity at around 1630 cm(-1)...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
https://www.readbyqxmd.com/read/28054005/data-of-aromatase-inhibitors-alone-and-in-combination-with-raloxifene-on-microarchitecture-of-lumbar-vertebrae-and-strength-test-in-femoral-diaphysis-of-vcd-treated-ovotoxic-mice
#4
Abul Kalam, Sushama Talegaonkar, Divya Vohora
Currently, the third generation aromatase inhibitors are the drugs of choice for treatment of early and advanced breast cancer in postmenopausal women. The negative impact of these drugs on bone health is the significant limiting factor during this therapy. Here we report the effect of two aromatase inhibitors viz. letrozole and exemestane alone and in combination with raloxifene on lumbar vertebrae and femoral diaphysis after one month of treatment but no discernible effects were observed on bone when tested by micro CT and strength test except in trabecular number which was reduced in lumbar vertebrae following letrozole and exemestane...
February 2017: Data in Brief
https://www.readbyqxmd.com/read/28045273/analysis-of-configuration-and-conformation-of-furanose-ring-in-carbohydrate-and-nucleoside-by-vibrational-circular-dichroism
#5
Tohru Taniguchi, Kie Nakano, Ryosuke Baba, Kenji Monde
A reliable and convenient method for determining the configuration and conformation of the furanose ring in carbohydrates and nucleosides by vibrational circular dichroism (VCD) spectroscopy is described. Diastereomeric pairs of several furanose monosaccharides and nucleosides were prepared, and their VCD spectra were analyzed. The results revealed that VCD spectroscopy elucidates the equibrated state of the furanose ring puckers, which is often difficult to study by other techniques.
January 3, 2017: Organic Letters
https://www.readbyqxmd.com/read/28019704/isolation-of-the-major-chiral-compounds-from-bubonium-graveolens-essential-oil-by-hplc-and-absolute-configuration-determination-by-vcd
#6
Mohammed El-Amin Said, Isabelle Bombarda, Jean-Valère Naubron, Pierre Vanloot, Marion Jean, Abdelkrim Cheriti, Nathalie Dupuy, Christian Roussel
The chirality issues in the essential oils (EOs) of leaves and flowers from Bubonium graveolens were addressed by chiral high-performance liquid chromatography (HPLC) with polarimetric detection and vibrational circular dichroism (VCD). The chemical compositions of the crude oils of three samples were established by gas chromatography / mass spectrometry (GC/MS). The well-known cis-chrysanthenyl acetate (1), oxocyclonerolidol (2), and the recently disclosed cis-acetyloxychrysanthenyl acetate (3), the three major chiral compounds, were isolated by preparative HPLC...
December 26, 2016: Chirality
https://www.readbyqxmd.com/read/28013359/comparison-of-engraftment-following-different-stem-cell-mobilization-modalities-in-patients-with-multiple-myeloma-treated-with-a-uniform-induction-regimen-containing-bortezomib-cyclophosphamide-and-dexamethasone
#7
Noam Benyamini, Irit Avivi, Eldad J Dann, Tsila Zuckerman, Noa Lavi, Tami Katz
Bortezomib-based induction followed by autologous stem cell transplantation is a common treatment for multiple myeloma (MM). Stem cell (SC) mobilization with granulocyte-colony stimulating factor (G-CSF) alone has become an alternative to G-CSF combined with chemotherapeutic agents. This study aimed to compare the efficacy of the two mobilization modalities following induction with a uniform regimen containing bortezomib, cyclophosphamide and dexamethasone (VCD). We retrospectively evaluated results of SC mobilization using either G-CSF alone or combined with high-dose cyclophosphamide (HD-CY) in MM patients after VCD induction...
December 24, 2016: Annals of Hematology
https://www.readbyqxmd.com/read/27995257/supramolecular-organization-of-perfluorinated-1h-indazoles-in-the-solid-state-using-x-ray-crystallography-ssnmr-and-sensitive-vcd-and-non-sensitive-mir-fir-and-raman-to-chirality-vibrational-spectroscopies
#8
María M Quesada-Moreno, Juan Ramón Avilés-Moreno, Juan Jesús López-González, Kane Jacob, Laure Vendier, Michel Etienne, Ibon Alkorta, José Elguero, Rosa M Claramunt
1H-Indazole derivatives exhibit a remarkable property since some of them form chiral supramolecular structures starting from achiral monomers. The present work deals with the study of three perfluorinated 1H-indazoles that resolve spontaneously as conglomerates. These conglomerates can contain either a pure enantiomer (one helix) or a mixture of both enantiomers (both helices) with an enantiomeric excess (e.e.) of one of them. The difficulty of the structural analysis of these types of compounds is thus clear...
January 4, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27973824/unusual-chiroptical-properties-of-the-cryptophane-222-skeleton
#9
Delphine Pitrat, Nicolas Daugey, Marion Jean, Nicolas Vanthuyne, Frank Wien, Laurent Ducasse, Nathalie Calin, Thierry Buffeteau, Thierry Brotin
Enantiopure cryptophane-222 derivative (1) devoid of substituents was obtained via high-performance liquid chromatography (HPLC) using chiral stationary phases. The chiroptical properties of 1 were determined from polarimetry, electronic circular dichroism (ECD), synchrotron radiation circular dichroism (SRCD), vibrational circular dichroism (VCD), and Raman optical activity (ROA) experiments and were compared to those of the cryptophane-A (2) derivative. Unusual polarimetric results were obtained for 1 in CHCl3 solvent as the sign of the optical rotation (OR) values changes in the nonresonance region above 365 nm, whereas no change was observed in the CH2Cl2 solvent...
December 15, 2016: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/27973781/vibrational-optical-activity-of-bodipy-dimers-the-role-of-magnetic-electric-coupling-in-vibrational-excitons
#10
Sergio Abbate, Torsten Bruhn, Gennaro Pescitelli, Giovanna Longhi
The vibrational exciton (VE) interpretation of intense bisignated couplets in vibrational circular dichroism (VCD) spectra of a pair of atropisomeric BODIPY (boron dipyrrin) dimers is discussed. The role of intrinsic magnetic moments is crucial to reproduce the different behaviors of quasi-isomeric BODIPY dimers with different aryl junction.
December 29, 2016: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/27960581/distribution-of-ocular-component-measures-and-refraction-in-brazilian-school-children
#11
Rodrigo Pessoa Cavalcanti Lira, Carlos Eduardo Leite Arieta, Thaís Helena Moreira Passos, Diana Maziero, Gustavo Lima do Valle Astur, Ítalo Fernandes do Espírito Santo, Ana Cláudia Bertolani, Luis Fernando Pozzi, Rosane Silvestre de Castro, Álvaro Antônio Bandeira Ferraz
PURPOSE: To describe ocular component values and refraction in 6-17-year-old school children in Campinas, Brazil. METHODS: To obtain a representative sample, a total of 1100 6-17-year-old public school students in Campinas, Brazil, were randomly selected and divided into groups according to median ages 6 years (range 5-7 years), 10 years (range 9-11 years), 14 years (range 13-15 years), and 17 years (range 16-18 years). Cycloplegic autorefraction and ocular biometry were performed on each child...
February 2017: Ophthalmic Epidemiology
https://www.readbyqxmd.com/read/27897329/molecules-in-molecules-fragment-based-method-for-the-calculation-of-chiroptical-spectra-of-large-molecules-vibrational-circular-dichroism-and-raman-optical-activity-spectra-of-alanine-polypeptides
#12
K V Jovan Jose, Krishnan Raghavachari
The molecules-in-molecules (MIM) fragment-based method has recently been adapted to evaluate the chiroptical (vibrational circular dichroism [VCD] and Raman optical activity [ROA]) spectra of large molecules such as peptides. In the MIM-VCD and MIM-ROA methods, the relevant higher energy derivatives of the parent molecule are assembled from the corresponding derivatives of smaller fragment subsystems. In addition, the missing long-range interfragment interactions are accounted at a computationally less expensive level of theory (MIM2)...
December 2016: Chirality
https://www.readbyqxmd.com/read/27892789/4-vinylcyclohexene-diepoxide-disrupts-sperm-characteristics-endocrine-balance-and-redox-status-in-testes-and-epididymis-of-rats
#13
Isaac A Adedara, Amos O Abolaji, Emmanuel O Ladipo, Ore J Fatunmibi, Ayodeji O Abajingin, Ebenezer O Farombi
OBJECTIVES: Exposure to 4-vinylcyclohexene diepoxide (VCD) was reported to induce testicular germ cell toxicity in rodents. However, there is paucity of information on the precise biochemical and molecular mechanisms of VCD-induced male reproductive toxicity. METHODOLOGY: This study investigated the influence of VCD on testicular and epidydimal functions following oral exposure of Wistar rats to VCD at 0, 100, 250 and 500 mg/kg for 28 consecutive days. RESULTS: Administration of VCD significantly decreased the body weight gain and organo-somatic indices of the testes and epididymis...
November 28, 2016: Redox Report: Communications in Free Radical Research
https://www.readbyqxmd.com/read/27869352/configurationally-stable-chiral-dithia-bridged-hetero-4-helicene-radical-cation-electronic-structure-and-absolute-configuration
#14
Bettina D Gliemann, Ana G Petrovic, Eva M Zolnhofer, Pavlo O Dral, Frank Hampel, Georg Breitenbruch, Philipp Schulze, Vijay Raghavan, Karsten Meyer, Prasad L Polavarapu, Nina Berova, Milan Kivala
A stable chiral hetero[4]helicene radical cation was synthesized and characterized by UV/Vis absorption and EPR spectroscopy, as well as X-ray crystallography. For the first time, a combination of chiroptical methods involving ECD, ORD, and VCD, supported by quantum mechanical predictions, enabled the elucidation of the absolute configuration of such open-shell helical species.
January 3, 2017: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/27832985/effects-of-raloxifene-against-letrozole-induced-bone-loss-in-chemically-induced-model-of-menopause-in-mice
#15
Abul Kalam, Sushama Talegaonkar, Divya Vohora
INTRODUCTION: The deleterious effects of letrozole, an aromatase inhibitor, used in the adjuvant treatment of breast cancer in postmenopausal women, on bone are well-documented and represent a major drawback to its clinical use. Raloxifene, a selective estrogen receptor modulator and a clinically approved anti-osteoporotic drug, has been recently demonstrated to be efficacious in women with breast cancer. The present study evaluated the effects of preventive and curative treatment with raloxifene on letrozole-induced alterations of bone microarchitecture and turnover markers in a chemically-induced menopause model in mice...
January 15, 2017: Molecular and Cellular Endocrinology
https://www.readbyqxmd.com/read/27830854/atropisomerism-in-3-arylthiazolidine-2-thiones-a-combined-dynamic-nmr-and-dynamic-hplc-study
#16
A Ciogli, S Vivek Kumar, M Mancinelli, A Mazzanti, S Perumal, C Severi, C Villani
Sterically hindered 3-arylthiazolidine-2-thiones were prepared by a solvent-free reaction with arylisothiocyanates and 1,4-dithiane-2,5-diol. Atropisomerism was observed in two compounds (3 and 4, aryl = 1-naphthyl and 2-methylnaphth-1-yl), whose rotational energy barriers were measured using dynamic NMR and dynamic HPLC. The experimental analyses were supported by DFT calculations. Thermally stable atropisomers were obtained by dehydration of compounds 3 and 4 and the absolute configuration of the atropisomers of compound 6 was determined by theoretical simulation of the ECD and VCD spectra...
November 10, 2016: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/27805191/vibrational-spectroscopy-as-a-direct-stereochemical-probe-for-polyhydroxylated-molecules
#17
F Passareli, A N L Batista, A J Cavalheiro, W A Herrebout, J M Batista Junior
A simple IR and VCD spectra-structure relationship is proposed for the determination of the relative and absolute configurations of polyhydroxylated molecules using a series of styryl-pyrones as model compounds. Spectral signatures identified for free molecules and acetonide derivatives may be used for stereochemical assignments of related molecules without the aid of quantum-chemical calculations.
November 16, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27801585/absolute-configuration-determination-of-2-3-dihydro-1h-5h-pyrazolo-1-2-a-pyrazoles-using-chiroptical-methods-at-different-wavelengths
#18
Eva Pušavec Kirar, Uroš Grošelj, Amalija Golobič, Franc Požgan, Stefan Pusch, Carina Weber, Lars Andernach, Bogdan Štefane, Till Opatz, Jurij Svete
A correlation between the absolute configuration and chiroptical properties of nonracemic 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles was studied. A series of 16 novel representatives were prepared by Cu-catalyzed [3 + 2] cycloadditions of racemic (Z)-2-benzylidene-5-oxopyrazolidin-2-ium-1-ides to tert-butyl (S)-(3-oxopent-4-yn-2-yl)carbamate, and their structures were determined by NMR, VCD, ECD, and X-ray diffraction. A clear correlation between the sign of specific rotation and configuration at position C(1) allows for easy determination of the absolute configuration of 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by ECD and NMR...
December 2, 2016: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27793768/cognitive-changes-across-the-menopause-transition-a-longitudinal-evaluation-of-the-impact-of-age-and-ovarian-status-on-spatial-memory
#19
Stephanie V Koebele, Sarah E Mennenga, Ryoko Hiroi, Alicia M Quihuis, Lauren T Hewitt, Mallori L Poisson, Christina George, Loretta P Mayer, Cheryl A Dyer, Leona S Aiken, Laurence M Demers, Catherine Carson, Heather A Bimonte-Nelson
Cognitive changes that occur during mid-life and beyond are linked to both aging and the menopause transition. Studies in women suggest that the age at menopause onset can impact cognitive status later in life; yet, little is known about memory changes that occur during the transitional period to the postmenopausal state. The 4-vinylcyclohexene diepoxide (VCD) model simulates transitional menopause in rodents by depleting the immature ovarian follicle reserve and allowing animals to retain their follicle-deplete ovarian tissue, resulting in a profile similar to the majority of perimenopausal women...
January 2017: Hormones and Behavior
https://www.readbyqxmd.com/read/27779841/reinvestigation-of-the-absolute-configurations-of-chiral-%C3%AE-mercaptoalkanones-using-vibrational-circular-dichroism-and-1-h-nmr-analysis
#20
Christiane Kiske, Svenja Nörenberg, Miriam Ecker, Xingyue Ma, Tohru Taniguchi, Kenji Monde, Wolfgang Eisenreich, Karl-Heinz Engel
The absolute configurations of chiral β-mercaptoalkanones were previously assigned on the basis of the (1)H NMR anisotropy method using (S)-2-methoxy-2-(1-naphthyl)propionic acid ((S)-MαNP) as the chiral auxiliary. This study presents a reinvestigation of the configurations of 4-mercapto-2-pentanone 1, 4-mercapto-2-heptanone 2, and 2-mercapto-4-heptanone 3. Enantiomers of 1, 2, and 3 were obtained by lipase-catalyzed hydrolyses of the respective acetylthioalkanones. Upon derivatization with (S)-MαNP, the configurations of the reaction products were deduced based on the order of the HPLC elution of the diastereoisomeric thioesters, assuming that the sector rule previously developed for secondary alcohols is also valid for thiols...
November 16, 2016: Journal of Agricultural and Food Chemistry
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