bluuebunny/crossref_metadata_2025 huggingface dataset:
One‐Pot Synthesis and Structure of Organochalcogen Halides with Mixed Valence States
Authors: Schulz Lang Ernesto , Casagrande Gleison Antônio , Manzoni de Oliveira Gelson , Ledesma Gabriela Nanci , Lemos Sebastião S. , Castellano Eduardo Ernesto , Abram Ulrich
Published: January 2006

Treatment of the diorganodichalcogenides PhEEPh (E = Se, Te) with one equivalent of elemental halogen (bromine or iodine) in methanol followed by addition of a sulfur donor and one more equivalent of the corresponding organochalcogen trihalide PhTeX3 affords the mixed‐oxidation‐state organochalcogen halides [PhEII(L)PhE′IVX4] (E = Se, Te; E′ = Te; X = Br, I; L = thiourea, tetramethylthiourea) in a one‐pot procedure. The X‐ray structural analyses of these compounds suggest a strong dependence of the formation of supramolecular assemblies on the nature of the halogen bonded to the tellurium atom. The halogen can induce intramolecular and intermolecular secondary interactions among the heavy atoms simultaneously and, in addition to Te···X and X···X secondary bonds, intramolecular interactions of the type Te···η6‐π‐aryl can be formed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A Cyclic Fc–Histidine Conjugate: Synthesis and Properties – Interactions with Alkali Metal Ions
Authors: Chowdhury Somenath , Schatte Gabriele , Kraatz Heinz‐Bernhard
Published: January 2006

The synthesis of the novel N,Nπ‐(ferrocenophane‐1,1′‐diyldicarbonyl)‐bridged histidine methyl ester 1 and of the acyclicbis(histidine methyl ester) derivative 3 are reported. The structure of 1 was studied in the solid state and in solution. The single‐crystal structure of 1 shows that both proximal ferrocenyl (Fc) carbonyl groups are syn with respect to each other, which is a new structural motif for Fc–amino acid conjugates. This new syn conformation allows effective binding to alkali metal cations. Binding is evaluated by cyclic voltammetry monitoring the halfwave potential of the Fc group. Cation binding causes a shift to lower potential (Na+ > Li+ > K+, Cs+). Upon binding, compound 1 shows selectivity towards Na+ ions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Spectroscopic Comparison of Dinuclear Ti+ and Ti2+ μ‐η1:η1 Dinitrogen Complexes with Cp*/Pentafulvene and Amine/Amide Ligation: Moderate versus Strong Activation of N2 (Eur. J. Inorg. Chem. 2/2006)
Authors: Studt Felix , Lehnert Nicolai , Wiesler Beatrix E. , Scherer Axel , Beckhaus Rüdiger , Tuczek Felix
Published: January 2006

The cover picture shows that Raman spectroscopy can reveal drastically different N−N stretching frequencies in dinuclear, dinitrogen‐bridged titanium complexes. In the article by F. Tuczek et al. on p. 291 ff., the recently synthesized complex [{(η5‐C5Me5)Ti[η6‐C5H4C(p‐tolyl)2]}2(μ‐η1:η1‐N2)] (1; R. Beckhaus et al., Eur. J. Inorg. Chem. 2005, 1003) is compared to the dinuclear (dinitrogen)titanium complex [{(Me3Si)2NTiCl(TMEDA)}2(μ‐η1:η1‐N2)] (3; R. Duchateau et al., J. Am. Chem. Soc. 1991, 113, 8986). With respect to 3 [ν(NN) = 1284 cm−1], 1 exhibits an unusually high N−N stretching frequency [ν(NN) = 1749 cm−1]. These spectroscopic differences reflect different degrees of dinitrogen activation, which are explained by the fact that only one of the N2 π*‐orbitals is occupied in 1, whereas both π*‐orbitals are occupied in 3.
From an Acyclic, Polyunsaturated Precursor to the Polycyclic Taxane Ring System: The [4+2]/[2+2+2] and [2+2+2]/[4+2] Cyclization Strategies
Authors: Chouraqui Gaëlle , Petit Marc , Phansavath Phannarath , Aubert Corinne , Malacria Max
Published: January 2006

A combination of a cobalt(I)‐mediated cyclotrimerization and a [4+2] reaction is described as a new entry into the ABC core of taxanes. The [4+2]/[2+2+2] and the [2+2+2]/[4+2] pathways both lead to the expected ABC core of the title compound. Mechanistic proposals are described to understand the formation of the side products during the [2+2+2] cycloaddition and to apply useful modifications of the highly substituted unsaturated precursors. Indeed, we demonstrate, for the first approach, that the substitution at the propargylic position has a dramatic influence on the cyclization. For the second sequence, we observe that the silicon group at the terminal position of the double bond can alter the chemoselectivity of the cycloaddition. In addition, the use of a temporary silicon tether in the [2+2+2] cycloaddition provides a rapid access to a highly elaborate molecule 38, which exhibits latent functionality for further synthetic transformations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A Convenient Synthesis of An Original, Bifunctional Chelator Based on an ON2S Ligand and its Coordination Chemistry with the Oxorhenium(V) Core
Authors: Le Gal Julien , Benoist Eric
Published: January 2006

A semi‐rigid, tetradentate, bifunctional chelator (BFC) for the oxorhenium core has been synthesised in five steps with an overall yield of 46 %. An aromatic amine is available for conjugation to a peptide through an isothiocyanate function. This BFC is the first amine‐functionalised tetradentate ligand containing both amido and thiol functionalities. Monooxorhenium complexes were readily prepared from both the bifunctional chelator and a β‐alanine‐conjugated system. These complexes were obtained in good yield and were fully characterised. Moreover, they were found to be stable to ligand‐exchange reactions.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Efficient Synthesis of a Variety of New Functionalized Oxacalixarenes by Ullmann Coupling Reactions
Authors: Yang Fei , Yan Liwei , Ma Kuoyan , Yang Li , Li Jihong , Chen Lijuan , You Jinsong
Published: January 2006

We have developed an efficient method to synthesize a new type of oxacalix[4]arenes containing nitrogen functional groups in a single step, through N,N‐dimethylglycine‐promoted Ullmann coupling reactions starting from aryl dibromides in yields of up to 37 %. With a aryl difluoride as substrate, a large, fully aromatic crown ether 8 could be obtained in 25 % yield. Further functionalization of the nitrogen functional groups in the cores of these oxacalixarenes may offer new opportunities for constructing desirable molecular architectures and a range of nitrogen‐based multidentate ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of the Benzo[b]fluorene Core of the Kinamycins by Arylalkyne–Allene and Arylalkyne–Alkyne Cycloadditions
Authors: González‐Cantalapiedra Esther , de Frutos Óscar , Atienza Carmen , Mateo Cristina , Echavarren Antonio M.
Published: January 2006

Arylalkyne–allene and arylalkyne–alkyne cycloadditions yields benzo[a]fluorenones, which are related to the tetracyclic core of the kinamycins. In the arylalkyne–alkyne cycloadditions, we found a rearrangement that produces benzo[a]fluorenones, in addition to the expected benzo[b]fluorenones. This rearrangement could be suppressed in the presence of phenol, which allowed the synthesis of 4,9‐dimethoxy‐2‐methyl‐11H‐benzo[b]fluoren‐11‐one in excellent yield.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Impact of voice on emotional judgment of faces: An event‐related fMRI study
Authors: Ethofer Thomas , Anders Silke , Erb Michael , Droll Christina , Royen Lydia , Saur Ralf , Reiterer Susanne , Grodd Wolfgang , Wildgruber Dirk
Published: January 2006

Emotional information can be conveyed by various means of communication, such as propositional content, speech intonation, facial expression, and gestures. Prior studies have demonstrated that inputs from one modality can alter perception in another modality. To evaluate the impact of emotional intonation on ratings of emotional faces, a behavioral study first was carried out. Second, functional magnetic resonance (fMRI) was used to identify brain regions that mediate crossmodal effects of emotional prosody on judgments of facial expressions. In the behavioral study, subjects rated fearful and neutral facial expressions as being more fearful when accompanied by a fearful voice as compared to the same facial expressions without concomitant auditory stimulus, whereas no such influence on rating of faces was found for happy voices. In the fMRI experiment, this shift in rating of facial expressions in presence of a fearfully spoken sentence was correlated with the hemodynamic response in the left amygdala extending into the periamygdaloid cortex, which suggests that crossmodal effects on cognitive judgments of emotional information are mediated via these neuronal structures. Furthermore, significantly stronger activations were found in the mid‐portion of the right fusiform gyrus during judgment of facial expressions in presence of fearful as compared to happy intonations, indicating that enhanced processing of faces within this region can be induced by the presence of threat‐related information perceived via the auditory modality. Presumably, these increased extrastriate activations correspond to enhanced alertness, whereas responses within the left amygdala modulate cognitive evaluation of emotional facial expressions. Hum Brain Mapp, 2006. © 2006 Wiley‐Liss, Inc.
Input source and strength influences overall firing phase of model hippocampal CA1 pyramidal cells during theta: Relevance to REM sleep reactivation and memory consolidation
Authors: Booth Victoria , Poe Gina R.
Published: January 2006

In simulation studies using a realistic model CA1 pyramidal cell, we accounted for the shift in mean firing phase from theta cycle peaks to theta cycle troughs during rapid‐eye movement (REM) sleep reactivation of hippocampal CA1 place cells over several days of growing familiarization with an environment (Brain Res 855:176–180). Changes in the theta drive phase and amplitude between proximal and distal dendritic regions of the cell modulated the theta phase of firing when stimuli were presented at proximal and distal dendritic locations. Stimuli at proximal dendritic sites (proximal to 100 μm from the soma) invoked firing with a significant phase preference at the depolarizing theta peaks, while distal stimuli (>290 μm from the soma) invoked firing at hyperpolarizing theta troughs. The input location‐related phase preference depended on active dendritic conductances, a sufficient electrotonic separation between input sites and theta‐induced subthreshold membrane potential oscillations in the cell. The simulation results predict that the shift in mean theta phase during REM sleep cellular reactivation could occur through potentiation of distal dendritic (temporo‐ammonic) synapses and depotentiation of proximal dendritic (Schaffer collateral) synapses over the course of familiarization. © 2006 Wiley‐Liss, Inc.
Neurogenesis in the adult hippocampus
Authors: Christie Brian R. , Cameron Heather A.
Published: January 2006

The dentate gyrus (DG) contains one of the few neuronal populations in the mammalian brain that are generated throughout life. Research into the regulation and function of adult neurogenesis continues its rapid growth in popularity. With the researcher new to the field in mind, we review the processes that together constitute adult neurogenesis and some of the methods most commonly used for studying these processes. © 2006 Wiley‐Liss, Inc.
Functional maturation of adult‐generated granule cells
Authors: Overstreet‐Wadiche Linda S. , Westbrook Gary L.
Published: January 2006

The excitability and connectivity of adult‐generated granule cells dictate to what extent newborn neurons participate in the hippocampal network. These functional parameters evolve as newborn cells mature and interact with the existing circuit. The progression of granule cell maturation during neonatal development appears to be reiterated in the adult, but with some caveats. New approaches to identify and track newborn neurons are revealing the timing of this process, as well as its sensitivity to activity‐dependent regulation. © 2006 Wiley‐Liss, Inc.
Gonadal hormone modulation of hippocampal neurogenesis in the adult
Authors: Galea Liisa A.M. , Spritzer Mark D. , Barker Jennifer M. , Pawluski Jodi L.
Published: January 2006

Gonadal hormones modulate neurogenesis in the dentate gyrus (DG) of adult rodents in complex ways. Estradiol, the most potent estrogen, initially enhances and subsequently suppresses cell proliferation in the dentate gryus of adult female rodents. Much less is known about how estradiol modulates neurogenesis in the adult male rodent; however, recent evidence suggests that estradiol may have a moderate effect on cell proliferation but enhances cell survival in the DG of newly synthesized cells but only when estradiol is administered during a specific stage in the cell maturation cycle in the adult male rodent. Testosterone likely plays a role in adult neurogenesis, although there have been no direct studies to address this. However, pilot studies from our laboratory suggest that testosterone up‐regulates cell survival but not cell proliferation in the DG of adult male rats. Progesterone appears to attenuate the estradiol‐induced enhancement of cell proliferation. Neurosteroids such as allopregnalone decrease neurogenesis in adult rodents, while pregnancy and motherhood differentially regulate adult neurogenesis in the adult female rodent. Very few studies have investigated the effects of gonadal hormones on male rodents; however, studies have indicated that there is a gender difference in the response to hormone‐regulated hippocampal neurogenesis in the adult. Clearly, more work needs to be done to elucidate the effects of gonadal hormones on neurogenesis in the DG of both male and female rodents. © 2006 Wiley‐Liss Inc.
Stress and adult neurogenesis
Authors: Mirescu Christian , Gould Elizabeth
Published: January 2006

Stress hormones have potent growth‐inhibiting effects on a variety of peripheral tissues. Consistent with this general function, stress has been shown to inhibit cell proliferation and, ultimately, neurogenesis in the hippocampus. This effect appears to be common across mammalian species, life stages, and most types of stressors. Although some evidence points to a role for glucocorticoids in mediating this effect, contradictory data exist. This review considers the growing literature on this subject with specific emphasis on paradoxical findings and the role of glucocorticoids in modulating adult neurogenesis. © 2006 Wiley‐Liss, Inc.
Environmental enrichment and voluntary exercise massively increase neurogenesis in the adult hippocampus via dissociable pathways
Authors: Olson Andrea K. , Eadie Brennan D. , Ernst Carl , Christie Brian R.
Published: January 2006

Environmental enrichment (EE) and voluntary exercise (VEx) have consistently been shown to increase adult hippocampal neurogenesis and improve spatial learning ability. Although it appears that these two manipulations are equivalent in this regard, evidence exists that EE and VEx affect different phases of the neurogenic process in distinct ways. We review the data suggesting that EE increases the likelihood of survival of new cells, whereas VEx increases the level of proliferation of progenitor cells. We then outline the factors that may mediate these relationships. Finally, we provide a model showing that VEx leads to the convergence of key somatic and cerebral factors in the dentate gyrus (DG) to induce cell proliferation. Although insufficient evidence exists to provide a similar model for EE, we suggest that EE‐induced cell survival in the DG involves cortical restructuring as a means of promoting survival. We conclude that EE and VEx lead to an increase in overall hippocampal neurogenesis via dissociable pathways, and should therefore, be considered distinct interventions with regard to hippocampal plasticity and associated behaviors. © 2006 Wiley‐Liss, Inc.
Opiates, psychostimulants, and adult hippocampal neurogenesis: Insights for addiction and stem cell biology
Authors: Eisch Amelia J. , Harburg Gwyndolen C.
Published: January 2006

Once thought to produce global, nonspecific brain injury, drugs of abuse are now known to produce selective neuroadaptations in particular brain regions. These neuroadaptations are being closely examined for clues to the development, maintenance, and treatment of addiction. The hippocampus is an area of particular interest, as it is central to many aspects of the addictive process, including relapse to drug taking. A recently appreciated hippocampal neuroadapation produced by drugs as diverse as opiates and psychostimulants is decreased neurogenesis in the subgranular zone (SGZ). While the role of adult‐generated neurons is not clear, their functional integration into hippocampal circuitry raises the possibility that decreased adult SGZ neurogenesis may alter hippocampal function in such a way as to maintain addictive behavior or contribute to relapse. Here, we review the impact of opiates and psychostimulants on the different stages of cell development in the adult brain, as well as the different stages of the addictive process. We discuss how examination of drug‐induced alterations of adult neurogenesis advances our understanding of the complex mechanisms by which opiates and psychostimulants affect brain function while also opening avenues for novel ways of assessing the functional role of adult‐generated neurons. In addition, we highlight key discrepancies in the field and underscore the necessity to move “beyond BrdU”––beyond merely counting new hippocampal cells labeled with the S phase marker bromodeoxyuridine––so as to probe mechanistic questions about how drug‐induced alterations in adult hippocampal neurogenesis occur and what the functional ramifications of alterations in neurogenesis are for addiction. © 2006 Wiley‐Liss, Inc.
Inhibition of neurogenesis interferes with hippocampus‐dependent memory function
Authors: Winocur Gordon , Wojtowicz J. Martin , Sekeres Melanie , Snyder Jason S. , Wang Sabrina
Published: January 2006

Rats treated with low dose irradiation, to inhibit adult hippocampal neurogenesis, and control rats were administered a nonmatching‐to‐sample (NMTS) task, which measured conditional rule learning and memory for specific events, and a test of fear conditioning in which a discrete CS was paired with an aversive US in a complex environment. Irradiated rats were impaired on the NMTS task when the intervals between sample and test trials were relatively long, and in associating the shock‐induced fear with contextual cues in the fear conditioning task. Irradiated rats were not impaired in learning the basic NMTS rule or in performing that task when the intervals between the sample and test trials were short. Nor were there group differences in conditioning the fear response to the CS in the fear conditioning task. The results, which extend the range of hippocampus‐dependent tasks that can be said to be vulnerable to the effects of neurogenesis suppression, support the hypothesis that new hippocampal cells generated in adulthood participate in a broad range of hippocampal functions. © 2006 Wiley‐Liss, Inc.
Gangliosides of the nuclear membrane: A crucial locus of cytoprotective modulation
Authors: Ledeen Robert W. , Wu Gusheng
Published: January 2006

The original concept of gangliosides as localized components of the plasma membrane has broadened in recent years with recognition of their presence in various intracellular pools as well. The nuclear envelope (NE), consisting of two unique membranes, is one such structure shown to contain members of the gangliotetraose family and possibly other sialoglycolipids. GM1 situated in the inner membrane of the NE is tightly associated with a Na+/Ca2+exchanger whose activity it potentiates in the transfer of Ca2+from nucleoplasm to the NE lumen. This is in contrast to Na+/Ca2+exchangers of the plasma membrane which bind GM1 less avidly or not at all. This is believed due to different isoforms of exchanger, and a difference in topology of the exchanger relative to GM1. Cultured neurons from mice genetically engineered to lack gangliotetraose gangliosides such as GM1 were highly vulnerable to Ca2+‐induced apoptosis. They were rescued to some extent by GM1 but more effectively by LIGA‐20, a membrane‐permeant derivative of GM1 that traverses the plasma membrane more effectively than GM1 and inserts into the NE. As further indication of Ca2+dysregulation, the mutant mice were highly susceptible to kainite‐induced seizures which were attenuated by LIGA‐20. This correlated with the ability of LIGA‐20 to cross the blood–brain barrier, enter brain cells, insert into the NE, and potentiate the nuclear exchanger. GM1 in the NE, in association with nuclear Na+/Ca2+exchanger, is thus seen as contributing to Ca2+regulation within the nucleus and in the process exerting a cytoprotective role. J. Cell. Biochem. 97: 893–903, 2006. © 2006 Wiley‐Liss, Inc.
Quantum‐chemical derivation of electro‐optical parameters for alkanes
Authors: Smirnov Konstantin S. , Bougeard Daniel
Published: January 2006

An approach for deriving the bond electro‐optical parameters (EOPs) of the bond polarizability model (BPM) from quantum‐chemical calculations is proposed. The approach was used to obtain the equilibrium and valence EOPs for the CH and CC bonds in saturated hydrocarbons from the results of the DFT calculations of small chain alkanes. The parameters derived are in the range of those found in the literature. The results of the study show that for this class of molecules the polarizability tensor can be constructed as the sum of the individual bond polarizability tensors thus indicating the validity of the BPM. The use of the parameters in the calculation of the Raman activity of the normal modes of 2‐methylbutane shows a good correlation between the data obtained in the DFT calculations and those with the BPM. Factors influencing the reliability and transferability of the parameters are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Vibrational spectroscopic studies, conformations and quantum chemical calculations of 3,3,3‐trifluoropropyl‐ silane and 3,3,3‐trifluoropropylsilane‐d3
Authors: Klaeboe Peter , Guirgis Gamil A. , Witkowski Witold A. , Horn Anne , Nielsen Claus J.
Published: January 2006

Infrared spectra of 3,3,3‐trifluoropropylsilane (CF3CH2CH2SiH3) and 3,3,3‐trifluoropropylsilane‐d3 (CF3 CH2CH2SiD3) were obtained in the vapour, liquid, and crystalline solid phases in the range 4000–50 cm−1. Additional spectra in argon matrices at 5 K were recorded before and after annealing to temperatures 20–34 K. Raman spectra of the compounds as liquids were recorded at various temperatures between 296 and 183 K and spectra of the amorphous and crystalline solids were obtained.

The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the two vapours were shock‐frozen on a cold finger at 78 K, they turned partly crystalline immediately. After subsequent annealing to 140–150 K, ca 7–9 Raman bands of both molecules present in the liquids vanished in the crystal. Similar variations in intensity were observed in the corresponding infrared spectra before and after annealing. The spectra revealed the existence of one conformer (anti) in the crystal.

From Raman intensity variations of three independent pairs of anti and gauche bands between 298 and 173 K for the parent compound, and 298 and 183 K for the deuterated analogue, the values ΔconfHo(gauche−anti) = 4.1 ± 0.3 kJ mol−1 for the parent compound and the same value for the deuterated species were obtained in the liquid state. Annealing experiments in the matrices show that the gauche bands vanish after annealing, demonstrating that the anti conformer also has the lower energy here and that the barrier to gauche → anti inter‐conversion is around 5–6 kJ mol−1. The spectra of both conformers have been interpreted in detail.

Ab initio and DFT calculations at the HF/6–311G**, B3LYP/6–311 G** and MP2/6–311 G** levels gave optimized geometries, infrared and Raman intensities and vibrational wavenumbers for the anti and gauche conformers. The conformational enthalpy difference derived from the calculations was between 6.0 and 4.1 kJ mol−1 with anti being the low energy conformer. Copyright © 2006 John Wiley & Sons, Ltd.
Experimental and theoretical Raman investigation on interactions of Cu(II) with histamine
Authors: Torreggiani Armida , Esposti Alessandra Degli , Tamba Maurizio , Marconi Giancarlo , Fini Giancarlo
Published: January 2006

A vibrational study of histamine (Hm), a small imidazole‐containing hormone involved in many biological processes, and its complexes with copper (II) was carried out at pH 9. Both the Raman and IR spectra present marker bands yielding information on the metal coordination sites of Hm and, as a consequence, on the main species existing in the system.

At basic pH Hm gives rise to two predominant complexes: a water‐insoluble polymeric species, [CuLH−1]n, and a monomer, [CuL] or [CuL2]. In the first the imidazole ring takes part in the Cu(II) coordination in a fully deprotonated form, whereas in the second the ring is in the tautomeric I form. In addition, the neutral aminic group participates in the Cu(II) chelation in both species, whereas some ClO4− ions complete the coordination number of Cu(II) to six only in the monomeric complex, probably by replacing H2O or OH− in the coordination sphere.

Finally, the Raman spectra were satisfactorily simulated with the aid of the results of theoretical calculations based on the Density Functional Theory, allowing a reliable prediction of the bands of the species supposed to exist in the system. Copyright © 2006 John Wiley & Sons, Ltd.
Dispersion‐compensated supercontinuum generation for ultrabroadband multiplex coherent anti‐Stokes Raman scattering spectroscopy
Authors: Kano Hideaki , Hamaguchi Hiro‐o
Published: January 2006

We have generated a dispersion‐compensated picosecond ultrabroadband supercontinuum light source at the sample position without using any additional compensator such as a prism pair or a grating pair. The dispersion‐compensated supercontinuum, which is obtained just by optimizing the length of a photonic crystal fiber, has been used as a Stokes laser source for ultrabroadband multiplex coherent anti‐Stokes Raman scattering (CARS) spectroscopy. Owing to an optimized temporal overlap between the narrowband pump and the Stokes supercontinuum pulses, a CARS signal has been obtained efficiently with a spectral coverage of more than 2800 cm−1. Furthermore, a vibrationally resonant CARS signal is observed not only when the pump pulse and the Stokes supercontinuum are temporally overlapped but also when the pump pulse follows the supercontinuum. It can be explained by an impulsive excitation of the vibrational coherence by the supercontinuum and a subsequent probe by a narrowband pump pulse. Using the dispersion‐compensated supercontinuum, we can perform not only the frequency‐domain multiplex CARS but also the time‐domain impulsive CARS measurement by controlling the delay time between the narrowband laser and the supercontinuum. Both these techniques can be applied to microspectroscopy in order to obtain the wide spectral range of vibrational resonances and the suppression of the nonresonant background. Copyright © 2006 John Wiley & Sons, Ltd.
Investigation of the low‐spin to high‐spin transition in a novel [Fe(pmea)(NCS)2] complex by IR and Raman spectroscopy and DFT calculations
Authors: Brehm Georg , Reiher Markus , Le Guennic Boris , Leibold Michael , Schindler Siegfried , Heinemann Frank W. , Schneider Siegfried
Published: January 2006

The X‐ray structures of the novel spin crossover complex [Fe(pmea)(NCS)2] with pmea = (bis[(2‐pyridyl)methyl]‐2‐(2‐pyridyl)ethylamin) were determined in its low‐spin (singlet, LS) and high‐spin state (quintet, HS) and compared with the optimized geometries produced by BP86 calculations. IR and Raman (λex = 514.5, 785 and 1064 nm) spectra were recorded at different temperatures between T = 298 K and T = 30 K. Most of the experimentally observed bands could be assigned unambiguously and discussed by comparison with the normal modes calculated for both spin states.

The detailed analysis of the temperature dependence of the band contours of specific modes provides strong evidence that significant changes of the inter‐molecular distances occur for all molecules when a certain fraction of the individual molecules has undergone the low‐spin (LS) to high‐spin (HS) transition.

The partition function for intra‐molecular vibrations was calculated for both spin states by considering all vibrational wavenumbers that were calculated. The vibration‐related entropy change connected with the LS to HS transition is determined via well‐established thermodynamic relations. For the title compound we found ΔSvib ≈ 40.3 J/(mol·K), which is about twice that determined for [Fe(phen)2(NCS)2]. Consequently, the sum of the purely electronic contribution (∼13.4 J/(mol·K)) and that of the intra‐molecular vibrations equals the average entropic driving force determined for a series of spin‐crossover complexes (∼50 J/(mol·K)). It is therefore most interesting to experimentally determine the entropy change for the complex investigated here and to find out whether this complex exhibits an unusually large entropy change upon the LS to HS transition. Copyright © 2006 John Wiley & Sons, Ltd.
Degenerate and two‐color resonant four‐wave mixing applied to the rotational characterization of high‐lying vibrational states of formaldehyde (Ã, 1A2)
Authors: Tulej M. , Meisinger M. , Knopp G. , Walser A. M. , Beaud P. , Gerber T. , Radi P. P.
Published: January 2006

Degenerate and two‐color resonant four‐wave mixing techniques (DFWM and TC‐RFWM) are applied to determine rotational constants of high‐lying vibrational levels in the first excited singlet state Ã(1A2) of formaldehyde. It has been demonstrated that the sensitivity of the spectroscopic technique is applicable to the low‐density environment of a supersonic molecular beam and to predissociating transitions displaying low fluorescence quantum yield. In addition, we take advantage of the superior selectivity of the double‐resonance method, TC‐RFWM, to isolate and assign transitions in the congested region of the (one‐color) DFWM spectra. The line positions of 25 well‐isolated transitions are determined in the $2_{0}^{2}5_{0}^{1}$ band and yield the rotational constants A, B, C and the origin νe. The accuracy of the constants is determined by performing the same procedure for the $2_{0}^{2}4_{0}^{1}$ band where literature data is available for comparison. Copyright © 2006 John Wiley & Sons, Ltd.
Quantitative polarization‐sensitive resonance CARS and resonance Raman spectroscopy on octaethylporphine
Authors: Koster J. , Popp J. , Schlücker S.
Published: January 2006

We present polarization‐sensitive (PS) multiplex coherent anti‐Stokes Raman scattering (CARS) spectra of octaethylporphine (OEP) in solution employing Q band resonance conditions. Several advantages of this four‐wave mixing technique compared with spontaneous resonance Raman (RR) spectroscopy are demonstrated. PS CARS spectroscopy allows the acquisition of high‐quality polarized vibrational spectra of this luminescent D2h symmetric free‐base porphyrin. From a quantitative CARS lineshape analysis, a set of accurate band parameters for the normal modes in the range 1510–1670 cm−1 is determined; in particular, individual spectral contributions from the nearly degenerate modes ν19 and ν2 can be differentiated and unambiguously assigned. The observed difference of π between the coherent phases of totally symmetric ag modes (ν11, ν2, ν10) and non totally symmetric b1g modes (ν19) confirms a correlation with normal mode symmetry. Using the CARS lineshape parameters, hypothetical polarized RR spectra for Q band excitation are generated: this enables a direct comparison with experimentally detected polarized RR spectra obtained with preresonant B band excitation. Major changes in spectral parameters such as intensity enhancements and depolarization ratios of prominent macrocycle modes due to the different electronic resonance conditions are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Protein secondary structure from deep‐UV resonance Raman spectroscopy
Authors: Huang Cheng‐Yen , Balakrishnan Gurusamy , Spiro Thomas G.
Published: January 2006

Raman spectra of proteins that are obtained with deep ultraviolet excitation contain resonance‐enhanced amide bands of the polypeptide backbone, as well as aromatic side chain bands. The amide bands are sensitive to conformation, and can be used to estimate the backbone secondary structure. UV Raman spectra are reported at 206.5 and 197 nm, for a set of 12 proteins with varied secondary structure content, and are used to establish quantitative signatures of secondary structure via least‐squares fitting. Amide band enhancement is greater at 197 nm, where basis spectra are established for β‐turn, as well as α‐helix, β‐sheet and unordered structures; the lower signal strength at 206.5 nm does not provide a reliable spectrum for the first of these. Application of these basis spectra is illustrated for the melting of apo‐myoglobin. The amide band positions and cross sections are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Ground state vibrational wave‐packet and recovery dynamics studied by time‐resolved CARS and pump‐CARS spectroscopy
Authors: Siebert T. , Schmitt M. , Gräfe S. , Engel Volker
Published: January 2006

Recent experiments on gaseous iodine and β‐carotene are analyzed within a wave‐packet description of femtosecond‐time resolved four‐wave mixing spectroscopy. Employing the same formalism, two different experimental setups, both established in the Kiefer group, are treated. In a transient four‐wave‐mixing (FWM) experiment, where two pulses interact simultaneously with the system, the interaction with a third time‐delayed pulse leads to light emission reflecting ground state vibrational dynamics in I2. On the other hand, delaying a FWM‐pulse sequence with respect to a single pump pulse interacting with β‐carotene yields a signal that is directly proportional to the population of a selected nuclear eigenstate in the electronic ground state. Thus, within this setup, it is possible to monitor ground‐state re‐population dynamics mode specifically. Copyright © 2006 John Wiley & Sons, Ltd.
Resonance Raman assignment of myeloperoxidase and the selected mutants Asp94Val and Met243Thr. Effect of the heme distortion
Authors: Brogioni Silvia , Feis Alessandro , Marzocchi Mario P. , Zederbauer Martina , Furtmüller Paul G. , Obinger Christian , Smulevich Giulietta
Published: January 2006

Resonance Raman (RR) spectra have been acquired for human myeloperoxidase (MPO), and its Met243Thr and Asp94Val mutants with different excitation wavelengths and in polarized light. The proteins were characterized as ferric, ferrous and ferric–CN complexes in order to study the heme configuration in various coordination, spin and oxidation states. Well‐defined spectra of the five‐coordinate high spin (ferrous), six‐coordinate high spin (ferric) and low spin (ferric–CN) species were obtained. The data allowed us to propose an almost complete assignment of the RR bands. The richness of the RR spectra of MPO is because of the activation of almost all the in‐plane skeletal modes observed for the Ni–octaethylporphyrin model compound, induced by the distortion of the heme imposed by the covalent links with the protein. The two mutants, which lost at least one of the covalent links between the protein and the heme group, were useful to determine the effect of the symmetry lowering of the heme group. Copyright © 2006 John Wiley & Sons, Ltd.
Surface enhanced Raman scattering (SERS)—a quantitative analytical tool?
Authors: Sackmann M. , Materny A.
Published: January 2006

Raman spectroscopy is a widely used analytical tool capable of providing valuable information about the chemical structure and composition of molecules. In order to detect substances also at a very low concentration levels, Surface Enhanced Raman Scattering (SERS) was introduced. The different amplification mechanisms result in extreme sensitivity, however, a quantitative use of SERS appears to be problematic. Especially, when deploying silver sols as SERS substrates, the reproducibility of the signal intensities for a given substance concentration is questionable. Experimental results of an investigation of this problem for low concentrations of adenine are presented. Comparison with results obtained for different SERS substrates by other authors reveals clearly different dependencies. Only in a very limited concentration range reproducible and therefore quantitatively utilizable data could be obtained. Copyright © 2006 John Wiley & Sons, Ltd.
Vibrational spectra of synthetic crandallite‐type minerals—optical and inelastic neutron scattering spectra
Authors: Breitinger D. K. , Brehm G. , Mohr J. , Colognesi D. , Parker S. F. , Stolle A. , Pimpl Th. H. , Schwab R. G.
Published: January 2006

The vibrational spectra of the synthetic minerals crandallite and goyazite MAl3(OH)6(HPO4)(PO4) (M = Ca and Sr) were studied by means of vibrational (IR and Raman) and inelastic neutron scattering (INS) spectrometries at room and low temperatures. The results were discussed taking into consideration the effects of different types of disorder (random distribution of PO4 and HPO4, orientational distribution with HPO4 and displacement of Ca in crandallite). The consequences of the resulting perturbed symmetry and of the non‐equivalence of the bridging µ‐OH groups in the Al2OH fragments were pointed out (complexity of the ν(Al2OH), δ(Al2OH) and γ(Al2OH) bands). The vibrations of the PO4 and HPO4 groups could be separated. Some aspects of the vibrational behaviour of the AlO2(OH)4 units and of the layers composed therewith were addressed. The translational modes of the interlayer cations Ca2+ and Sr2+ could be observed; the findings support the suggested displacement of Ca in crandallite. Copyright © 2006 John Wiley & Sons, Ltd.
Raman scattering of acoustical modes of silicon nanoparticles embedded in silica matrix
Authors: Ivanda M. , Hohl A. , Montagna M. , Mariotto G. , Ferrari M. , Crnjak Orel Z. , Turković A. , Furić K.
Published: January 2006

The Raman scattering from acoustical phonons of silicon quantum dots in glass matrix was investigated. Two peaks that correspond to symmetric and quadrupolar spheroidal vibrations were found. A model calculation for in‐ and off‐resonance scattering conditions was used, which considered the homogeneous broadening due to interaction with matrix and the inhomogeneous broadening due to particle size distribution. A strong dependence of the light‐to‐vibration coupling coefficient on the particles size was needed for fitting the Raman data. This result suggests that resonance with electronic transitions of the silicon nanoparticles is important for excitation at 514.5 nm. The size distribution obtained from the Raman data is in agreement with the results of high‐resolution transmission electron microscopy. Copyright © 2006 John Wiley & Sons, Ltd.
Continuous‐wave solid‐state Raman laser for spectroscopic applications
Authors: Lisinetskii V. A. , Grabtchikov A. S. , Apanasevich P. A. , Schmitt M. , Kuschner B. , Schlücker S. , Orlovich V. A.
Published: January 2006

The experimental and theoretical investigations of a solid‐state Raman laser operating in the continuous‐wave regime are described. The Raman laser represents the single resonant cavity with a Raman crystal. The theoretically predicted operation threshold is in agreement with that observed experimentally. The Raman conversion efficiency of the Stokes radiation is close to 5%. The analysis of temporal fluctuations of the output Stokes signal shows its super‐Gaussian statistics near the threshold. The output Stokes radiation was used for the measurement of the spontaneous Raman spectrum of CCl4. Copyright © 2006 John Wiley & Sons, Ltd.
Resonance Raman spectra of hydroxyphenyl squaraines: acid–base versus aggregation equilibria
Authors: Lopes José Guilherme S. , Farani Régis A. , de Oliveira Luiz Fernando C. , Santos Paulo S.
Published: January 2006

The optical and resonance Raman spectra (RR) of bis(phloroglucinol)squaraine (I) and bis(resorcinol)squaraine (II) were investigated, revealing that the equilibria between the neutral and anionic species present in solution explain the experimental observations much better than the previously proposed aggregation equilibria. In particular, the RR spectra were invaluable to assign characteristic modes of (I) and its monoanion, since the tuning of the excitation line to the electronic transition band of the neutral or monoanionic specie leads to the enhancement of the respective modes that are exclusive of each species. In addition, small angle X‐ray scattering (SAXS) experiments with (I) did not show any evidence of aggregation. Copyright © 2006 John Wiley & Sons, Ltd.
The excited‐state geometry of 1‐hydroxy‐2‐ acetonaphthone: a resonance Raman and quantum chemical study
Authors: Szeghalmi A. V. , Engel V. , Zgierski M. Z. , Popp J. , Schmitt M.
Published: January 2006

1‐Hydroxy‐2‐acetonaphthone (HAN), an intramolecular proton transfer system, was investigated in the present study by means of quantum chemical calculations and resonance Raman spectroscopy. To determine the Franck–Condon parameters, a time‐dependent approach for the analysis of the resonance Raman spectra was applied. About 18 vibrational modes were found to be involved in the initial dynamics of HAN upon photo excitation. Moreover, the excited‐state geometry of HAN was optimized at the CASSCF level of theory and the displacement parameters were determined. A very good agreement between the theoretical and experimentally derived parameters was obtained. The vibrations with the highest displacements correspond to stretching and in‐plane deformation modes of the naphthalene ring and the conjugated carbonyl group, while the OH stretching mode exhibits no observable enhancement. Hence, a general molecular rearrangement takes place upon photo excitation, where the intramolecular oxygen–oxygen distance reduces corresponding to a redistribution of the electron density. Copyright © 2006 John Wiley & Sons, Ltd.
Raman and infrared spectroscopic mapping of human primary intracranial tumors: a comparative study
Authors: Krafft Christoph , Sobottka Stephan B. , Schackert Gabriele , Salzer Reiner
Published: January 2006

Intracranial tumors are neoplasias of brain tissue or other tissue inside the skull. Cryosections of the three most frequent primary intracranial tumors—gliomas, meningeomas and schwannomas—were prepared on calcium fluoride windows and studied by both Raman spectroscopy and infrared (IR) spectroscopy. Spectroscopic maps were recorded by sequential acquisition of spectra in a raster pattern. Cluster analyses on selected wavenumber regions were applied for evaluation of these data sets. Raman spectroscopic contributions of proteins including collagen and hemoglobin were identified in cluster centroids, as were nucleic acids and lipids including cholesterol, cholesterol ester (CE) and phosphatidylcholine (PC). Moreover, hydroxyapatite and tricalciumphosphate could be identified as markers for calcification. The spatial distributions of these spectral properties were visualized in pseudocolor Raman and IR maps representing the cluster memberships. The prospects of both methods are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Probing self‐associated structures of the solute molecule, acrylonitrile, the solvent molecule 2Cl‐phenol and their binary complexes via concentration‐dependent Raman study and DFT calculation
Authors: Srivastava S. K. , Ojha Animesh K. , Sinha P. K. , Asthana B. P. , Singh Ranjan K.
Published: January 2006

Raman study of CN‐stretching mode of acrylonitrile and ring‐breathing mode of 2Cl‐phenol was made in the binary mixture of (acrylonitrile + 2Cl‐phenol) at different molar ratios of the two components. Raman spectra were recorded in the different spectral regions, 990–1070 cm−1 and 2170–2300 cm−1. Ring‐breathing mode of 2Cl‐phenol exhibited two components, which were attributed to the neat and self‐associated dimer of 2Cl‐phenol molecules. The self‐associated structure of the dimer was obtained by geometry optimization. Other structures, which were calculated, include self‐associated structure of acrylonitrile and the hydrogen‐bonded complex of (acrylonitrile + 2Cl‐phenol). All the geometry optimizations were made using density functional theory (DFT) and B3LYP functional employing the 6–31 + G(d,p) basis set. The variations of the linewidth and the peak position with concentration are explained on the basis of a model, which includes both the effect of concentration fluctuation in a microscopic volume and the influence of concentration‐dependent microviscosity based on a model proposed recently by our group. Copyright © 2006 John Wiley & Sons, Ltd.
Determination of the amide I Raman tensor for the antiparallel β‐sheet: application to silkworm and spider silks
Authors: Tsuboi Masamichi , Kubo Yoshiko , Akahane Kiso , Benevides James M. , Thomas George J.
Published: January 2006

The amide I Raman tensor corresponding to the antiparallel β‐sheet structure in proteins has been determined by polarized Raman microspectroscopy of fowl feather rachis using polarized Raman spectra excited in the near‐infrared (785 nm). For a Raman tensor principal axis system (XYZ), in which X is perpendicular to the plane of the pleated β‐sheet, Y is in the plane of the sheet and perpendicular to the direction of the polypeptide chain, and Z is parallel to the direction of the polypeptide chain, the principal tensor components (αXX, αYY, αZZ) are found to satisfy the following relationships: R1 ≡ αXX/αZZ = 0.32 and R2 ≡ αYY/αZZ = 3.48. With this Raman tensor determination, we show that semiquantitative estimates of the total antiparallel β‐sheet content in β‐rich proteins can be extracted from polarized Raman intensity measurements on the amide I marker of the β‐sheet occurring near 1664 cm−1. We demonstrate this approach for the β‐rich silk proteins of the silkworm and spider. Copyright © 2006 John Wiley & Sons, Ltd.
Spectroscopy of Raman‐shifted solitons in photonic‐crystal fibers
Authors: Serebryannikov E. E. , Hu Ming‐Lie , Wang Ching‐Yue , Li Yan‐Feng , Wang Zhuan , Chai Lu , Ren Xiaomin , Dukel'skii K. V. , Khokhlov A. V. , Shevandin V. S. , Kondrat'ev Yu. N. , Zheltikov A. M.
Published: January 2006

While femtosecond nonlinear Raman techniques typically deal with packets of vibrational quantum states in molecular systems, the technique proposed and implemented in this work uses the results of spectroscopic measurements to reconstruct the temporal structure of short‐pulse wavepackets undergoing continuous frequency downshifting owing to the Raman effect in special optical fibers. Our numerical simulations and experimental results demonstrate that the temporal structure and time dynamics of solitons in photonic‐crystal fibers can be conveniently reconstructed from spectral measurements performed at the output of the fiber. Copyright © 2006 John Wiley & Sons, Ltd.