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PubMed1998

Tacrolimus (FK506) in failed cyclosporin A therapy in endogenous posterior uveitis.

Tacrolimus (FK506) is effective in Japanese endogenous posterior uveitis (EPU), but there is limited data on its role in refractory EPU where cyclosporin A (CsA) toxicity/resistance develops. This open prospective clinical study aimed to assess the efficacy and adverse effects of low-dose FK506 therapy in western patients with refractory EPU where CsA resistance or toxicity has developed. Patients with CsA resistant/toxic EPU were started on low-dose (< 0.10 mg/kg/day) FK506 therapy. Immunosuppressive efficacy was assessed by visual acuity, binocular indirect ophthalmoscopy (BIO) scores, and change in clinical features. Adverse effects were assessed by routine biochemical tests (including serum creatinine) and symptoms. Seven patients (13 eyes), aged (mean +/- SD) 37.5 +/- 14.8 years, were recruited with previous CsA nephrotoxicity as the main indication and prior duration of EPU of (mean +/- SD) 13.1 +/- 7.3 years. Behçet's disease was the commonest diagnosis. FK506 therapy was maintained at 0.06 +/- 0.02 mg/kg/day, trough level of 8.7 +/- 1.8 ng/ml, in combination with low-dose prednisolone (0.11 +/- 0.04 mg/kg/day) in all patients for a mean duration of 8.7 months (range 1.0-17.7). From baseline (for 11 eyes with meaningful follow-up), visual acuity was maintained in nine eyes and BIO score improved in nine eyes. No major adverse effects developed, with only a 7.5 +/- 6.5% maximum increase in serum creatinine in patients with previous CsA-induced nephrotoxicity. Minor adverse effects (especially mild hyperglycaemia and neurological symptoms) were common and usually well tolerated, except for two patients in whom drug withdrawal was necessary, thus producing therapeutic failure. Low-dose FK506 is effective in refractory EPU as CsA-rescue therapy, and should be considered earlier in the evolution of refractory EPU.

Adult↗
PubMed2003

A populationwide coalescent analysis of Icelandic matrilineal and patrilineal genealogies: evidence for a faster evolutionary rate of mtDNA lineages than Y chromosomes.

Historical inferences from genetic data increasingly depend on assumptions about the genealogical process that shapes the frequencies of alleles over time. Yet little is known about the structure of human genealogies over long periods of time and how they depart from expectations of standard demographic models, such as that attributed to Wright and Fisher. To obtain such information and to examine the recent evolutionary history of mtDNA and Y-chromosome haplotypes in the Icelandic gene pool, we traced the matrilineal and patrilineal ancestry of all 131,060 Icelanders born after 1972 back to two cohorts of ancestors, one born between 1848 and 1892 and the other between 1798 and 1742. This populationwide coalescent analysis of Icelandic genealogies revealed highly positively skewed distributions of descendants to ancestors, with the vast majority of potential ancestors contributing one or no descendants and a minority of ancestors contributing large numbers of descendants. The expansion and loss of matrilines and patrilines has caused considerable fluctuation in the frequencies of mtDNA and Y-chromosome haplotypes, despite a rapid population expansion in Iceland during the past 300 years. Contrary to a widespread assumption, the rate of evolution caused by this lineage-sorting process was markedly faster in matrilines (mtDNA) than in patrilines (Y chromosomes). The primary cause is a 10% shorter matrilineal generation interval. Variance in the number of offspring produced within each generation was not an important differentiating factor. We observed an intergenerational correlation in offspring number and in the length of generation intervals in the matrilineal and patrilineal genealogies, which was stronger in matrilines and thus contributes to their faster evolutionary rate. These findings may have implications for coalescent date estimates based on mtDNA and Y chromosomes.

Alleles↗
PubMed1984

Evolution of child psychiatric teamwork in a somatic hospital.

This paper outlines the evolution of child psychiatric team work within the context of a general hospital. It focuses especially on the professional challenges and systemic problems arising during this 8 year long process. The question of what happens when two cultures meet in the same arena is discussed, and the process whereby a minority becomes a reality in a well-established majority system is described. Special attention is devoted to those principles appearing to play a major role in the evolutionary process. Prominent among these are: (1) operating within the already established; (2) transforming the 'ugly duckling into a swan', and (3) breaking into the established. The paper concludes with a brief discussion of the problems associated with maintaining enthusiasm in the team, scapegoating, and 'burn out'.

Child↗
PubMed1992

Extracellular enzymes: gene regulation and structure function relationship studies.

The first conclusion that one could make from the literature covered in this section is that most single mutations in subtilisin BPN'n do not cause major structural alterations. Even multiple mutations, though they may cause local minor perturbations at each of the altered sites, do not affect the overall structure to a large degree. Bott and Ultsch (1986) observed that the subtilisin BPN' structure is very tolerant of single mutations, and this tolerance may have been necessary for survival of the enzyme during the course of evolution. This structural tolerance is not all that surprising if one considers that the structure of subtilisin Carlsberg is very similar to that of subtilisin BPN' while the protein sequences differ by 31%. A superposition of the 274 alpha-carbon atoms of the two enzymes gives a root mean square (rms) deviation of 0.053 nm, a value indicating significant structural similarity (McPhalen and James 1988). Furthermore, the fungal enzyme proteinase K, which is classified as part of the subtilisin family, has approximately 38-40% sequence homology with bacilli subtilisins, particularly in the catalytic site and substrate-binding regions (Betzel et al. 1988). For these sequence-homology regions there is also a structural similarity indicated by a least squares superposition of alpha-carbons giving an rms deviation of 0.11 nm (Betzel et al. 1988). Thermitase, also a member of the subtilisin family, has 47% sequence homology to subtilisin BPN' (Gros et al. 1989). If the best 203 alpha-carbon atoms are superposed, then an rms deviation of 0.05 nm is obtained (Gros et al. 1989). Apparently a significant amount of sequence variation still allows for overall structural similarities in the subtilisin family of enzymes. Though the overall structure of subtilisin is not easily perturbed by single or even multiple mutations, it is clear from the evidence reviewed here that single mutations can lead to very significant effects on the catalytic efficiency, substrate preference, and stability of the enzyme. Analyzing the structural alterations in subtilisin mutants will lead to an understanding of the molecular effects of the mutations at the atomic level. This understanding enables investigators to model and predict the effects of other substitutions, and allows them to focus their efforts on those mutants that are most likely to have the desired properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1985

Kidney and liver levels of some major, minor and trace elements in two Ontario communities.

The contents of Ag, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Th, Ti and Zn in 143 autopsied liver and kidney specimens from two Ontario communities (Kingston and Ottawa) were determined using the techniques of inductively-coupled plasma--atomic emission spectrometry, and electrothermal atomization--atomic absorption spectrometry coupled with hydride evolution (As, Se), reduction--aeration (Hg), or solvent extraction (Pb). The majority of samples came from individuals older than 50 y. In general, the data for the various elements were independent of age or sex but showed some dependence on location for elements such as Cu, Fe, K, Mg, Mn, Na, P, Se and Zn. Despite these differences the elemental values of the liver and kidney samples from both the communities were within the normal range.

Adolescent↗
PubMed1996

Small SiC grains and a nitride grain of circumstellar origin from the Murchison meteorite: implications for stellar evolution and nucleosynthesis.

We report the results of SIMS isotopic analyses of carbon, nitrogen, oxygen, and silicon made on 849 small (approximately 1 micrometer) individual silicon carbide grains from the Murchison meteorite. The isotopic compositions of the major elements carbon and silicon of most grains (mainstream) are similar to those observed in larger grain studies suggesting an AGB star origin of these grains. In contrast, the trace element nitrogen shows a clear dependency on grain size. 14N/15N ratios increase with decreasing grain size, suggesting different stellar sources for grains of different size. Typically observed 14N/15N ratios in the small grains of this study are approximately 2700, clearly larger than the values expected from model calculations of AGB stars. In addition to the three dredge-up episodes characteristic for the evolution of AGB stars, extra-mixing of CNO-processed matter in low mass AGB stars appears to be a promising possibility in order to explain the high 14N/15N ratios of the small circumstellar SiC grains. A small fraction of grains shows a silicon isotopic signature not observed in larger circumstellar SiC grains from Murchison. Their stellar origin is still uncertain. The minor type A, B, Y, and X grains were found to be present at a level of a percent, which is similar to their abundance in the larger-grain SiC separates from Murchison. Oxygen isotopic compositions are normal within the experimental uncertainties of several 10%, indicating that oxygen of stellar origin is rare or even absent in the SiC grains. We conclude that most of the oxygen is a contaminant which was introduced into the SiC grains after their formation, e.g., during sample processing in the laboratory. We identified a nitride grain, most likely Si3N4 with little carbon, with highly anomalous isotopic compositions (12C/13C = 157 +/- 33, 14N/15N = 18 +/- 1, delta 29 Si = -43 +/- 56%, delta 30 Si = -271 +/- 50%). The isotopic patterns of carbon, nitrogen, and silicon resemble those of the rare SiC X grains suggesting that these two rare constituents of circumstellar matter formed in the same type of stellar source, namely, Type II supernovae.

Carbon↗
PubMedDate not supplied

EGF and EGF-r immunoexpression in Sjögren's syndrome secondary to rheumatoid arthritis. Correlation with EBV expression?

Minor labial salivary gland biopsies from 25 patients with secondary Sjögren's syndrome (SS) suffering from rheumatoid arthritis and from 11 patients complaining of ocular dryness associated with rheumatoid arthritis without proven SS, were studied for the immunohistochemical expression of Epidermal Growth Factor (EGF) and its receptor (EGF-r). Minor labial salivary glands from 11 healthy individuals were used as the control. Furthermore, the results were correlated with data retrieved from a previous study on EBV expression by the in situ hybridization method in the same specimens. In 16/25 cases of secondary SS the epithelial duct cells expressed both EGF and EGF-r, particularly in the areas of lymphoepithelial lesion and tissue destruction. Eleven of these cases expressed a positive EBV hybridization signal. In contrast, only 3/11 patients with ocular dryness and 2/11 cases from the group of healthy individuals showed immunoreactivity for EGF/EGF-r. A positive EBV signal was detected in 3/11 and 1/11 of these cases, respectively. These results indicate that EGF and EGF-r may play a crucial role in the evolution of the disease under the constant influence of EBV, which seems to up-regulate the expression of the EGF/EGF-r system.

Adult↗
PubMed2005

Systematic classification of alleles of the glycophorin A (MN blood group) gene.

Ten alleles (five M and five N alleles) of the MN blood group system with normal antigenicity were found by sequencing the glycophorin A (GPA) gene. This study demonstrates the systematic classification of these alleles to major or minor variations of the standard alleles. GPA-specific fragments ranging from 150 to 3.8 kb in length were amplified from the templates, and exons 1-7 and introns 1-6 were sequenced. The data were analyzed phylogenetically to classify these alleles into major groups or clusters. The ten alleles were grouped into four major clusters M10X (M101-M103), M20X (M201 and M202), N10X (N101-N104) and N20X (N201), where 'X' represents a digit indicating minor variations. This grouping was supported by phylogenetic analysis. The cluster system of GPA alleles is highly informative for genetic screening.

Alleles↗
PubMed2004

Ovca1 regulates cell proliferation, embryonic development, and tumorigenesis.

Loss of OVCA1/DPH2L1 correlates with ovarian and breast cancer. To study its in vivo role, we generated Ovca1 mutant alleles in mice. Ovca1 heterozygotes spontaneously develop cancer. Ovca1 mutant mice die during embryonic development and at birth with developmental delay and defects in multiple organ systems. Cell proliferation defects were observed in Ovca1 mutant mouse embryonic fibroblasts (MEFs). p53 deficiency can rescue these Ovca1 mutant MEF proliferation defects and partially rescue Ovca1 mutant embryonic phenotypes. Furthermore, Ovca1; p53 double heterozygotes developed tumors quicker than p53 heterozygotes and with an increased carcinoma incidence. Multiple tumor burden in Ovca1 heterozygotes that were also p53 deficient was significantly higher than in p53 homozygous mutants. These in vivo findings demonstrate that Ovca1 is a tumor suppressor that can modify p53-induced tumorigenesis and suggest that it acts as a positive regulator for cell cycle progression. The close linkage of OVCA1 and p53 on human Chromosome 17 suggests that coordinated loss may be an important mechanism for the evolution of ovarian, breast, and other tumor phenotypes.

Animals↗
PubMed1993

Genetic heterogeneity among isolates of Ross River virus from different geographical regions.

The RNase T1 maps of 80 isolates of Ross River virus from different regions of mainland Australia and the Pacific Islands were compared. Four different clusters of isolates with greater than an estimated 5 to 6% diversity at the nucleotide level were found. There was a pattern of differences between eastern and western Australian strains; however, the pattern was disturbed by overlaps and incursants. Pacific Islands isolates belonged to the eastern Australian topotype. Our findings suggest that certain genetic types of Ross River virus predominate in different geographical regions. In contrast, populations of other important Australian arboviruses (Murray Valley encephalitis, Kunjin, and Sindbis viruses) are distributed across the Australian continent as minor variants of one strain. Our data also show that in one region, strains of Ross River virus with identical RNase T1 maps circulate during both years when epidemics occur and years when they do not. This finding suggests that Ross River virus epidemics are not dependent on the introduction or evolution of new strains of the virus. Two strains, belonging to the eastern Australian topotype, were isolated in Western Australia. It is likely that viremic humans or possibly domestic livestock travelling by aircraft were responsible for this movement.

Australia↗
PubMed1996

The postconcussional syndrome reappraised.

Despite the apparently benign nature of mild head injury, reflected by the short post-traumatic amnesia duration, relative absence of CNS signs and brief hospital stay, a significant number of patients report persistent symptomatology over the weeks or months afterwards. Largely subjective in nature, such symptom clusters are termed the postconcussion syndrome. The discrepancy between the predominantly subjective complaints and negative examination findings has generated uncertainty and debate about the respective causation roles of organic and psychogenic factors. Over the past 30 years evidence for organic brain changes has accumulated through studies of cerebral circulation, neuropsychological deficits, evoked potential recordings and neuroimaging. This paper reviews data from two UK prospective studies of the evolution and course of postconcussional symptomatology using parallel psychosocial, neuropsychiatric, quantitative EEG and brainstem auditory evoked potential recordings. Changes in theta power occurred early with resolution within 10 days. Prolonged brainstem evoked response I-V intervals were seen in between 27% and 46% of patients. Symptom chronicity noted in a minority of people (13%) was associated with a high prevalence of brainstem dysfunction, while the degree of QEEG recovery appeared to relate to the intensity of early symptom reaction to the trauma. Levels of perceived stress at the time of the injury or afterwards were not related to symptom formation, but chronic social difficulties were a feature of the 21% of patients who initially improved but had a late exacerbation of symptoms between 6 weeks and 6 months after the trauma.

Adolescent↗
PubMed1993

[The drug treatment of postoperative pain].

The study, conducted on 40 patients with pain resulting from "minor" general surgery, for the purpose of evaluating the efficacy and tolerability of ST-679 (administered in a single oral dose of 1200 mg in 20 patients) and to compare them with those of paracetamol (administered in a single oral dose of 1000 mg in 20 patients), demonstrated that the new drug was active on all recorded parameters and superior to the reference drug. The evaluation of the evolution of pain, performed using the Scott-Huskisson visual analog scale, evidenced that the maximum analgesic efficacy of ST-679 is reached after 1 hour and 15 minutes from assumption and remains unaltered until the final observation (6 hours). The paracetamol registers maximum analgesic efficacy after 30 minutes, but does not remain constant for the entire observation period. All the other parameters evaluated (variation in pain intensity, peak of analgesic activity and total remission of pain) are significantly favorable to ST-679. The tolerability of ST-679 was very good and better than the reference drug.

Acetaminophen↗
PubMed1993

Quaternary environments and the evolution of primates in East Asia, with notes on two new specimens of fossil Cercopithecidae from China.

Primate faunas in East Asia since the mid-Tertiary have undergone a series of major changes in response to a complex sequence of environmental changes. As a consequence of the Himalayan orogeny and the rapid, episodic uplift of the Tibetan plateau, the climate of East Asia during the late Tertiary became monsoonal and thus more strongly seasonal. This led to the expansion of seasonal tropical forests and, in some areas, grasslands. During the Pleistocene, the climatic consequences of continued rapid uplift of the Tibetan plateau and other land masses (e.g. the Qinling mountains) were combined with those of glaciations, resulting in dramatic climatic oscillations between warm-humid and cold-dry phases. The contraction of tropical environments that began in the late Tertiary reached its peak at the last glacial maximum (LGM) and was responsible for the decline in the distribution and diversity of hominoids in East Asia. Cercopithecids, which were only minor elements of the late Tertiary primate faunas, colonized tropical, subtropical and temperate environments in the Pleistocene and were able to reradiate into those environments after the LGM. The abilities of monkeys to populate a wide range of terrestrial environments (eurytopy) contrast with those of apes, which are restricted to tropical forest environments (stenotopy).

Animals↗
PubMed2003

Evolution of the immunomodulatory role of the heat shock protein gp96.

In mammals, certain heat shock proteins (hsps) participate in specialized responses to stressors associated with pathogens or tumors, and as such, act as agents of immune surveillance interacting with both innate and adaptive immunity. We are investigating the conservation of this role throughout the class of vertebrates. We have shown that in Xenopus as in mammals, gp96, the major resident of the endoplasmic reticulum, generates MHC-restricted thymus-dependent immunity in vivo and CR in vitro against minor histocompatibility (H) antigens. By as yet unclear mechanisms that may involve classical MHC-unrestricted cytotoxic CD8+ T cells, gp96 also elicits peptide-specific responses against MHC-class I-negative tumors in adult frogs that may involve cytotoxic NK, MHC-unrestricted CD8+ T and NK/T cells. In naturally MHC class I-deficient but immunocompetent Xenopus larvae, gp96 also generates an innate type of anti-tumor response that is independent of chaperoned peptides. Finally, in a subset of Xenopus sIgM+ B cells, a substantial fraction of gp96 is directed to the cell surface by an active process that is upregulated by bacterial stimulation. This may allow gp96 to access the extracellular compartment without necrosis. Given the dual abilities of gp96 to chaperone antigenic peptides and to modulate innate immune responses, we propose that stimulated B cells that are up-regulating surface gp96 can directly interact with antigen presenting cells (APC) and/or T helper (Th) cells to trigger or amplify immune responses.

Adjuvants, Immunologic↗
PubMed2000

Molecular phylogenetic analysis of the Pneumoroidea (Orthoptera, Caelifera): molecular data resolve morphological character conflicts in the basal acridomorpha.

A key transition in the evolution of the insect suborder Caelifera (Orthoptera; Insecta) was from predominantly non-angiosperm-feeding basal lineages to the modern acridomorph fauna (grasshoppers and related insects). However, because of conflicts in the distribution of several complex morphological characters, the relationships of the presumed intermediates, and in particular of the superfamily Pneumoroidea, are presently unclear. We undertook a phylogenetic study of representatives of all of the transitional acridomorph families using mitochondrial and nuclear DNA sequences. No support for pneumoroid monophyly was obtained from nonparametric bootstrap analysis. Furthermore, adopting a maximum-likelihood approach, specific hypotheses of relationships within the Pneumoroidea were firmly rejected using parametric bootstrapping and Kishino-Hasegawa tests. The results indicate that the Pneumoroidea are at best a grade. This distinction implies that the evolution of the proposed pneumoroid synapomorphies, femoro-abdominal stridulation and simple male genital structure, might previously have been misinterpreted as cases of single character gains or losses within lineages. Reconstructions of character states for the femoro-abdominal stridulation indicate that, in fact, multiple losses or gains are equally likely. An important implication of our findings is that, in grasshoppers, auditory tympana may have evolved before stridulation, supporting the argument that the original function of tympana may have been related not to conspecific communication but to predator detection. Overall, the results of this study emphasize the high information content of these minor groups (in this case, the four intermediate families under consideration contain only 0.2% of extant orthopteran species diversity). Our analyses also demonstrate the advantages of model-based methods in analyzing systematic problems and, in particular, of the importance of testing specific phylogenetic hypotheses when a priori support for groupings (e.g., from nonparametric bootstrapping) is marginal.

Animals↗
PubMed2006

Utility of mitochondrial DNA barcodes in species conservation.

Molecular tools are a standard part of many conservation studies and can be informative at many different levels of analysis, although there are inherent limitations and strengths of different genes or parts of genes to inform specific questions. Animal DNA barcodes, 600- to 800-base-pair segments of the mitochondrial gene cytochrome oxidase I, have been proposed as a means to quantify global biodiversity. Although mitochondrial (mt) DNA has a long history of use at the species level, recent analyses suggest that the use of a single gene, particularly mitochondrial, is unlikely to yield data that are balanced, universally acceptable, or sufficient in taxonomic scope to recognize many species lineages. Mitochondrial and nuclear genomes have different patterns of evolution and modes of inheritance, which can result in very different assessments of biodiversity. The ramifications of choosing a particular definition of species (species concept) need to be carefully considered because current efforts have designated DNA barcodes as the universal species concept without demonstrating its superiority over preexisting concepts. The results of such a barcoding paradigm may include a failure to recognize significant portions of biodiversity or nuclear/mitochondrial mixed lineages and could spuriously focus conservation resources on populations with relatively minor mtDNA divergence. DNA barcodes are most likely to provide potentially useful information for groups that are already well studied, and such taxa do not constitute the majority of biodiversity or those in most need of research attention. DNA barcode-length sequences are an important source of data but, when used alone or out of context, may offer only a fraction of the information needed to characterize species while taking resources from broader studies that could produce information essential to robust and informed conservation decisions.

Biodiversity↗
PubMed2006

[Evaluation of the Chêneau brace in adolescent idiopathic scoliosis].

OBJECTIVE: We aimed to evaluate the Chêneau brace in the orthopedic treatment of adolescent idiopathic scoliosis to better determine the indications under which it could be prescribed. MATERIALS AND METHODS: This was a retrospective study including 63 patients treated by Chêneau brace for adolescent idiopathic scoliosis between 1997 and 2006. The Cobb angles of the curves in the frontal and sagittal planes as well as rotations and rib hump were measured at the beginning of treatment, with the brace, at the end of treatment and 2 years after discontinuing the brace. A variation of+/-10 degrees in angle was selected to judge the results. RESULTS: At the end of the treatment, 25.4% of the curves were improved and 60.3% stabilized, with 14.3% aggravated; 5 patients (7.9%) required surgery. At 2 years, the reduction in angle was 1.8 degrees, on average. The best results were obtained for the lumbar and dorsolumbar curves. A significant improvement was noted for the dorsal curves; the major double curves are not as accessible to the treatment. For curves whose initial angle was less than 30 degrees , an initial reduction of higher than 50% with the brace presented the best improvement at the end of the follow-up. We note a significant reduction of the rib hump but not accompanied by a reduction of rotation. Finally, we note a deleterious effect in the sagittal curves, with a slight flatness of the spinal profile. CONCLUSION: The continuous wearing of the Chêneau brace can stabilize the evolution of adolescent idiopathic scoliosis, apart from the forms with major double curves, which are not as accessible to the treatment. However, the improvement comes at the price of a slight flatness of the curves of the spine in the sagittal plane. The loss of the correction after discontinuing the brace is minor. We emphasize, therefore, the necessity to monitor the sagittal aspect of the spine as well as the possibility of early treatment, strict surveillance and prolonged follow-up.

Adolescent↗
PubMed2006

Study of polarized IR spectra of the hydrogen bond system in crystals of styrylacetic acid.

We have investigated the polarized IR spectra of the hydrogen bond system in crystals of trans-styrylacetic acid C(6)H(5)CHCHCH(2)COOH, and also in crystals of the following three deuterium isotopomers of the compound: C(6)H(5)CHCHCH(2)COOD, C(6)H(5)CHCHCD(2)COOH and C(6)H(5)CHCHCD(2)COOD. The spectra were measured at room temperature and at 77K by a transmission method. The spectral studies were preceded by determination of the X-ray crystal structure. Theoretical analysis of the results concerned linear dichroic effects, the H/D isotopic and temperature effects, observed in the solid-state IR spectra of the hydrogen and of the deuterium bond, at the frequency ranges of the nu(OH) and the nu(OD) bands, respectively. Basic spectral properties of the crystals can be interpreted satisfactorily in terms of the "strong-coupling" theory, when based on a hydrogen bond dimer model. This model sufficiently explained not only a two-branch structure of the nu(OH) and the nu(OD) bands, and temperature-induced evolution of the crystalline spectra, but also the linear dichroic effects observed in the band frequency ranges. A vibronic mechanism was analyzed, responsible for promotion of the symmetry-forbidden transition in the IR for the totally symmetric proton stretching vibrations in centrosymmetric hydrogen bond dimers. It was found to be of minor importance, when compared with analogous spectral properties of arylcarboxylic acid, or of cinnamic acid crystals. These effects were ascribed to a substantial weakening of electronic couplings between the hydrogen bonds of the associated carboxyl groups and the styryl radicals, associated with the separation of these groups in styrylacetic acid molecules by methylene groups in the molecules.

Chemical Phenomena↗