bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorylation of serine 262 in the gap junction protein connexin-43 regulates DNA synthesis in cell-cell contact forming cardiomyocytes
Authors: Doble Bradley W. , Dang Xitong , Ping Peipei , Fandrich Robert R. , Nickel Barbara E. , Jin Yan , Cattini Peter A. , Kardami Elissavet
Published: December 2003

Mitogenic stimulation of cardiomyocytes is associated with decreased gap junction coupling and protein kinase C (PKC)-mediated phosphorylation of the gap junction protein connexin43 (Cx43). Identification of and interference with the amino acid(s) that becomes phosphorylated in response to stimulation are important steps towards defining the relationship between Cx43 phosphorylation and cell cycle. Using immunoblotting and phosphospecific antibodies we were able to show that serine-262 (S262) on Cx43 becomes phosphorylated in response to growth factor or PKC stimulation of cardiomyocytes. To examine the effect of Cx43, S262 phosphorylation and cell-cell contact (and/or coupling) on DNA synthesis, we overexpressed wild-type (wt) or mutant Cx43, carrying a S262-to-alanine (S262A, simulating the unphosphorylated state) or a S262-to-aspartate (S262D, simulating constitutive phosphorylation) substitutions in cultures of cell-cell contact forming or isolated cardiomyocytes. Overexpression of wt-Cx43 caused a significant decrease in DNA synthesis irrespective of the presence of cell-cell contact. In cell-cell contact forming cultures, the S262D mutation reversed while the S262A mutation increased the inhibitory effect of Cx43. In the absence of cell-cell contact, the S262-Cx43 mutations had no significant effect on Cx43 inhibition of DNA synthesis. Dye-coupling, evaluated by scrape-loading, indicated increased gap junction permeability in S262A (compared to wt or S262D) overexpressing myocytes. We conclude that Cx43 inhibits cardiomyocyte DNA synthesis irrespectively of cell-cell contact or coupling. Cell-cell contact, and possibly gap junction-mediated communication is required, however, in order to reverse Cx43 inhibition of DNA synthesis by S262 phosphorylation.
Forespore membrane assembly in yeast: coordinating SPBs and membrane trafficking
Authors: Shimoda Chikashi
Published: December 2003

In the yeasts Schizosaccharomyces pombe and Saccharomyces cerevisiae, sporulation involves de novo synthesis of forespore membrane (FSM) within the cytoplasm of mother cells. The FSM ultimately becomes the plasma membrane of the developing ascospores. Several protein components of the FSM have been identified. Visualization of these proteins has demonstrated the dynamic nature of the genesis and development of the FSM. It begins to develop at the differentiated outer plaque of the spindle pole bodies (SPBs) and extends outwards, encapsulating each of the haploid nuclei produced by meiosis. Several coiled-coil proteins are specifically recruited to the SPBs and play indispensable roles in FSM assembly. Temporal and spatial coordination of meiotic nuclear divisions and membrane assembly is of special importance. Comparison of the processes of FSM assembly in these yeasts shows that the basic mechanism has been conserved, even though the individual proteins involved are often different. Understanding these dynamic aspects of yeast sporulation will help to elucidate a general mechanism for the cellularization of cytoplasm containing multiple nuclei.
Reliving, emotions, and fragmentation in the autobiographical memories of veterans diagnosed with PTSD
Authors: Rubin David C. , Feldman Michelle E. , Beckham Jean C.
Published: December 2003

Fifty veterans diagnosed with posttraumatic stress disorder (PTSD) each recalled four autobiographical memories: one from the 2 years before service, one non‐combat memory from the time in service, one from combat, and one from service that had often come as an intrusive memory. For each memory, they provided 21 ratings about reliving, belief, sensory properties, reexperiencing emotions, visceral emotional responses, fragmentation, and narrative coherence. We used these ratings to examine three claims about traumatic memories: a separation of cognitive and visceral aspects of emotion, an increased sense of reliving, and increased fragmentation. There was evidence for a partial separation of cognitive judgments of reexperiencing an emotion and reports of visceral symptoms of the emotion, with visceral symptoms correlating more consistently with scores on PTSD tests. Reliving, but not fragmentation of the memories, increased with increases in the trauma relatedness of the event and with increases in scores on standardized tests of PTSD severity. Copyright © 2004 John Wiley & Sons, Ltd.
Multiple sclerosis: Cytokine receptors on oligodendrocytes predict innate regulation
Authors: Cannella Barbara , Raine Cedric S.
Published: December 2003

Multiple sclerosis (MS) is an immune‐mediated demyelinating condition in which numerous soluble mediators have been implicated. We have extended the repertoire of cytokines studied in MS tissue by examining interleukin (IL‐4), IL‐6, IL‐10, IL‐12, IL‐18, interferon (IFNγ), and their receptors and have compared patterns with those seen in normal subjects and other neurological diseases (OND). Expression was evaluated by immunocytochemistry and Western blots. Remarkably, oligodendrocytes expressed all the cytokine receptors examined, particularly Th2‐type, constitutively in normal subjects and upregulated in disease. Microglial cells also expressed cytokine receptors at similar levels. Cytokine expression was invariably a feature of microglial cells, except for IL‐10, which was exclusively astrocytic. Oligodendrocytes did not display cytokines, except for low levels of IL‐18. Although no pattern was specific for MS, most molecules were upregulated in MS and OND. Downstream JAK/STAT molecules were correspondingly upregulated. Cytokine receptors on oligodendrocytes (and microglia), and their corresponding ligands on microglia (and astrocytes), may implicate paracrine/autocrine regulation and may bespeak innate immunity in the central nervous system.
Analgesic triptan action in an animal model of intracranial pain: A race against the development of central sensitization
Authors: Burstein Rami , Jakubowski Moshe
Published: December 2003

We have shown that the development of cutaneous allodynia (exaggerated skin sensitivity) during migraine is detrimental to the anti‐migraine action of the 5HTIB/ID receptor agonists known is triptans. Because cutaneous allodynia is a manifestation of sensitization of central trigeminovascular neurons, we examined whether triptan treatment can intercept such sensitization before its initiation or after its establishment in our rat model for cutaneous allodynia induced by intracranial pain. Single‐unit recordings were obtained from spinal trigeminal neurons that proved to received convergent inputs from the dura and facial skin. The effects of sumatriptan (300 μg/kg i.v.) on central sensitization induced by topical application of inflammatory soup (IS) on the dura were determined when the drug was administered either 2 h after IS (late intervention) or at the same time as IS (early intervention). Late sumatriptan intervention counteracted two aspects of central sensitization: dural receptive fields, which initially expanded by IS, shrunk back after treatment; neuronal response threshold to dural indentation, which initially decreased after IS, increased after sumatriptan. On the other hand, late sumatriptan intervention did not reverse other aspects of central sensitization: spontaneous firing rate and neuronal response magnitude to skin brushing which initially increased after IS, remained elevated after sumatriptan; response threshold to heating of the skin, which initially dropped after IS, remained low after sumatriptan. Early sumatriptan intervention effectively blocked the development of all aspects of central sensitization expected to be induced 2 h after IS application: dural receptive fields did not expand; neuronal response threshold to dural indentation and skin stimulation did not decrease; spontaneous firing rate did not increase. The early treatment results suggest that triptan action provides a powerful means of preventing the initiation of central sensitization triggered by chemical stimulation of meningeal nociceptors. The late treatment results suggest that triptan action is insufficient to counteract an already established central sensitization. Thus, triptan action appears to be exerted directly on peripheral rather than central trigeminovascular neurons. Ann Neurol 2004;55:000–000
Defeating migraine pain with triptans: A race against the development of cutaneous allodynia
Authors: Burstein Rami , Collins Beth , Jakubowski Moshe
Published: December 2003

For many migraine patients, triptan therapy provides complete pain relief in some attacks but not in others. Here, we tested whether the success of triptan therapy is hindered in the presence of cutaneous allodynia (pain resulting from a nonnoxious stimulus to normal skin), a phenomenon we previously described develop gradually during the course of the migraine attack in more than 70% of patients. We studied migraine patients repeatedly on three visits to the clinic: in the absence of migraine (baseline), within the first hour of one attack, or at 4 hours from onset of another attack. Presence or absence of allodynia was determined based on differences between migraine and baseline pain thresholds to mechanical and thermal stimulation of periorbital skin. In 31 patients, we studied 34 migraine attacks that were associated with allodynia at the time of triptan treatment and 27 attacks that were not. Within 2 hours of triptan treatment, patients were rendered pain‐free in 5 of 34 (15%) of allodynic attacks versus 25 of 27 (93%) of nonallodynic attacks. Treating migraine attacks 1 hour (early) or 4 hours (late) after the onset of pain was equally ineffective in inducing a pain‐free state in the presence of allodynia, and equally effective in the absence of allodynia. For patients susceptible to allodynia during the attack, triptan therapy was by far more likely to provide complete pain relief if administered before rather than after the establishment of cutaneous allodynia. Patients who never developed allodynia were highly likely to be rendered pain‐free by triptan therapy anytime after the onset of pain. We conclude that the probability of consistent pain‐free outcome increases drastically if triptan therapy is vigilantly timed to precede any signs of cutaneous allodynia. Ann Neurol 2004;55:000–000
Multiple sclerosis in US veterans of the Vietnam era and later military service: Race, sex, and geography
Authors: Wallin Mitchell T. , Page William F. , Kurtzke John F.
Published: December 2003

We identified 5,345 cases of multiple sclerosis (MS) among US veterans who first entered military service between 1960 and 1994, and who were “service‐connected” for MS by the Department of Veterans Affairs (VA). Two controls per case were matched on age, date of service entry, and branch of service. Available for service and VA files were demographic and military data for 4,951 cases and 9,378 controls. Versus white men, relative risk of MS was significantly higher for all women, at 2.99 for whites, 2.86 for blacks, and 3.51 for those of other races. This was a significant increase from our prior series of veterans of World War II and the Korean Conflict, where white women had a relative risk of 1.79. Risk for black men was higher now (0.67 vs 0.44), while other men remained low (0.30 vs 0.22). Residence at service entry in the northern tier of states had a relative risk of 2.02 versus the southern tier, which was significantly less than the 2.64 for the earlier series. Residence by individual state at birth and service entry for white men further supported this decreasing geographic differential. Such marked changes in geography, sex, and race in such a short interval strongly imply a primary environmental factor in the cause or precipitation of this disease.
Effect of subthalamic deep brain stimulation on the function of the urinary bladder
Authors: Seif Christoph , Herzog Jan , van der Horst Christof , Schrader Bettina , Volkmann Jens , Deuschl Guenther , Juenemann Klaus‐Peter , Braun Peter M.
Published: December 2003

Detrusor hyperreflexia is a relevant clinical symptom for patients suffering from Parkinson's disease. In a series of 16 patients, we demonstrated that subthalamic deep brain stimulation has a significant and urodynamically recordable effect leading to a normalization of pathologically increased bladder sensibility.
Complex phenotypes in an Indian family with homozygous SCA2 mutations
Authors: Ragothaman Mona , Sarangmath Nagaraja , Chaudhary Shashi , Khare Vishwamohini , Mittal Uma , Sharma Sangeeta , Komatireddy Sreelatha , Chakrabarti Subhabrata , Mukerji Mitali , Juyal Ramesh C. , Thelma B. K. , Muthane Uday B.
Published: December 2003

We describe a consanguineous Indian family having spinocerebellar ataxia type 2 (SCA2) expansions with complex phenotypes (early‐onset, dopa‐responsive parkinsonism, ataxia and retinitis pigmentosa). The two probands having homozygous SCA2 mutations presenting with early‐onset dopa‐responsive parkinsonism without ataxia develop dyskinesias within a year of starting levodopa. Their siblings, heterozygous for SCA2 mutations, had retinitis pigmentosa with or without ataxia. Approximately 38% of family members with SCA2 mutations were asymptomatic.
Tactile awareness and limb position in neglect: Functional magnetic resonance imaging
Authors: Valenza Nathalie , Seghier Mohamed L. , Schwartz Sophie , Lazeyras François , Vuilleumier Patrik
Published: December 2003

We studied a patient with right parietal damage for whom tactile stimuli on the right/ipsilesional hand (projecting to the intact left hemisphere) were extinguished from awareness during double simultaneous stimulation, when his right hand was positioned in the left/contralesional space. This demonstrates the role of an egocentric spatial reference frame in attention that can determine awareness of stimuli despite intact sensory pathways. Using functional magnetic resonance imaging to elucidate the neural correlates of such perceptual extinction, we found that limb position modulated neural responses to tactile stimuli at early cortical stages (SI) in the intact hemisphere. Activity in bilateral middle frontal gyri also was modulated by limb position and may contribute to integrate sensory inputs into a supramodal, egocentric representation of space.
Non‐Enzymatic Synthesis of Polysaccharides, Nucleosides and Nucleic Acids and the Origin of Self‐Reproducing Systems
Authors: Schramm G. , Grötsch H. , Pollmann W.
Published: December 2003

Compounds containing free amino, hydroxyl or carbonyl groups can be activated by reaction with polyphosphate ester. If the compounds contain a second functional group, polycondensations are possible; e.g. amino acids → polypeptides, carbohydrates → polysaccharides, nucleotides → polynucleotides. In the presence of polyadenylic acid, polymerization of uridylic acid is speeded up tenfold. This mutual effect of complementary nucleotide strands constitutes the experimental basis for a hypothesis concerning the terrestrial origin of systems capable of self‐reproduction.
Chemical Reactions in the Atmosphere
Authors: Harteck P. , Reeves R. R.
Published: December 2003

Chemical reactions in the upper atmosphere may be investigated by sending rockets into the region of interest or by simulating conditions in the laboratory. Ultraviolet solar radiation dissociates and ionizes all types of particles present in the chemosphere. This results in recombination reactions of radicals, charge transfers, and chemical reactions of ions with neutral particles. In addition bimolecular reactions between neutral particles and reactions involving excited molecules take place.
Liquid Ion‐Exchange Technology
Authors: Kunin R. , Winger A. G.
Published: December 2003

Liquid ion exchangers have certain advantages over conventional solid ion exchange resins. For example, they make possible the removal of ionic species from solutions of relatively high concentration. Because of favorable distribution factors, the number of stages needed for a practical degree of extraction is usually low. Typical liquid ion exchangers are amines or alkyl phosphoric acids in the molecular weight range 250–500.
Some Organic Sulfur Compounds in Vegetables and Fodder Plants and their Significance in Human Nutrition
Authors: Virtanen Artturi I.
Published: December 2003

Many plants that serve for human nutritional purposes contain compounds from which physiologically active substances are formed by enzymic reactions. Usually such compounds, and the enzymes which react with them, are located in different cells, so that the active substances are formed only on crushing the plant: Examples are the lachrymatory factor and the antimicrobial substances formed from the different cysteine‐S‐oxides of the onion and garlic, as well as the goitrogenic compounds formed from the thioglucosides occuring in the Brassica species.
Ring Substitutions and Secondary Reaktions of Aromatic‐Metal π‐Complexes, Part I
Authors: Plesske Klaus
Published: December 2003

π‐Complexes of aromatic compounds with transition metals display aromatic characteristics. This is shown, among other things, by the fact that many such compounds undergo aromatic substiution reactions. A survey of substitutions and secondary reactions in such systems is given.
Prephenic Acid: Properties and the Present Status of its Synthesis
Authors: Plieninger H.
Published: December 2003

Prephenic acid is an intermediate in the biosynthesis of aromatic compounds. Its synthesis is made difficult by the fact that it is a cyclohexadienol which is easily aromatized by acids and bases. Experiments aimed at its synthesis have led to an as yet inseparable mixture of a little prephenic acid, epiprephenic acid and dihydroprephenic acid (as‐Ba‐salt). Comparison with model compounds indicated that the tertiary carboxyl group and the hydroxyl group are in cis relationship.
Electrophilic Substitutions at Saturated Carbon Atoms
Authors: Köbrich G.
Published: December 2003

The results obtained in recent years from investigations into the mechanisms of electrophilic substitution reaction at sp3‐hybridized carbon atoms are reviewed.
The Patening of Chemical Inventions in the Federal Republic of Germany
Authors: Vossius V.
Published: December 2003

Under German Patent Law, the patenting of chemical inventions is subject to special rules which need not be observed with inventions in the mechanical field. These rules will be discussed in detail.
Special Properties of the Sugars in Cardioactive Glycosides
Authors: Reichstein T.
Published: December 2003

Striking differences are observed when the sugar components of digitaloid lactones ( as well as of two additional minor groups of substances) are compared with those of the other glycosides in higher plants: non‐digitaloid glycosides almost always contain one or more of the following eight sugars as a structural unit: D‐glucose, D‐glucuronic acid, D‐xylose, L‐arabinose, D‐galactose, D‐galacturonic acid, L‐fucose, and L‐rhamnose. Oligosaccharide moieties almost always contain hexoses “on the inside”. i.e. linked directly onto the aglycone, and pentoses and methyl pentoses “on the outside”. Oligosaccharide moieties containing more than two sugars often appears to be branched. Cardioactive glycosides ( and two related minor groups of substances) chiefly contain only two sugars of the eight listed, viz. D‐glucose and L‐rhamnose. Very often numerous other sugars are found, particularly hexamethyloses. Oligosaccharide moieties always contain the hexose (D‐glucose) “on the outside”. As far as is known, oligosaccharide moieties with more than two sugars are always built up linearly.
Carbonic Acid Derivatives from Formamides
Authors: Kühle E.
Published: December 2003

Starting from a few known synthese employing formamide/acid chloride adducts or the formamide chlorides derived therefrom, new routes leading to aromatic isocynodichlorides, iminochlorothioformates, and organic thiocyanates are described. The respective reaction mechanisms are briefly discussed.
Valence Isomerizations in Compounds with Strained Rings
Authors: Vogel E.
Published: December 2003

Among the many molecular rearrangements that may occur in compounds with strained rings, valence (or valence bond) isomerizations have recently received special attention. Relief of strain in energy‐rich small or medium‐sized rings is the driving force behind these predominantly thermal (pyrolysis) reactions. In many instances, valence isomerizations must be considered as multicenter rearrangements (with six‐ or four‐membered cyclic transition states). This mechanism can be regarded as firmly established for Cope rearrangements, as well as for intracyclic diene syntheses and diene cleavages of strained rings, with which this paper deals.
Reactive Dyes Containing Vinylsulfonyl Groups
Authors: Heyna J.
Published: December 2003

Compounds and dyes containing vinylsulfonyl groups or groupings which readily yield vinylsulfonyl groups possess a marked ability to add onto many compounds containing active hydrogen under alkaline conditions. They also react with natural substances of high molecular weight, e.g. wool and cellulose, which contain amino‐ or hydroxyl groups. These reactions lead to the formation of strong covalent bonds between the reactants. As a result of this finding, reactive dyes for nitrogenous and cellulose fibers have been developed.
Syntheses in the 3‐Aminoquinazol‐4‐one and 3‐Aminobenzotriazin‐4‐one Series
Authors: Petersen S. , Herlinger H. , Tietze E. , Siefken W.
Published: December 2003

Among the derivatives of 3‐aminoquinazol‐4‐one and 3‐aminobenzotriazin‐4‐one are compounds with narcotic, sedative, analgetic, and muscle‐relaxant properties. Of special interest are compounds with one or several urethane groups and those substituted in the 3‐position by a morpholine moiety.
Cyclooligomerization of Butadiene and Transition Metal π‐Complexes
Authors: Wilke G. , Bogdanovič B. , Borner P. , Breil H. , Hardt P. , Heimbach P. , Herrmann G. , Kaminsky H.‐J. , Keim W. , Kröner M. , Müller Herbert , Müller Ernst Willi , Oberkirch W. , Schneider J. , Stedefeder J. , Tanaka K. , Weyer K. , Wilke G.
Published: December 2003

Advances in the fields of synthesis and reactions of some medium‐sized hydrocarbon rings are reported and in connection therewith on novel π‐complexes of transition metals. Catalytic syntheses yield 1,5,9‐cyclododecatriene, 1,5‐cyclooctadiene, and 1,5‐cyclodecadiene either from butadiene or from butadiene and ethylene. The reactions proceed very readily.
Recent Developments in Organotin Chemistry
Authors: Neumann W. P. , Burkhardt G. , Heymann E. , Kleiner F. , König K. , Niermann H. , Pedain J. , Schick R. , Sommer R. , Weller H.
Published: December 2003

New synthetic methods developed in the field of organotin compounds since 1959 are reviewed. The use of alkyl aluminum compounds brings an advance in the preparation of tetraalkyltin derivatives, alkyltin halides, and alkyltin hydrides. Organotin hydrides offer new possibilities for the production of monomeric and polymeric organotin compounds. Diethyltin and diphenyltin, which are obtained by catalytic dehydrogenation of the respective dialkyltin dihydrides, are cyclic compounds. – The literature since 1959 is reviewed.
Chemistry and Biochemistry of Insect Hormones
Authors: Karlson P.
Published: December 2003

Insect hormones attracted the interest of endocrinologists only comparatively recently. This is partly due to the fact that an equivalent of sex hormones – the classical hormones of vertebrate physiology – is unknown in insects. Castration has no marked effect on the secondary sexual characters. Insect hormones act primarily on developmental processes; the metamorphosis hormone, ecdysone, is the best studied. Recent investigations have shown that ecdysone has the empirical formula C27H44O6 and belongs to the streroids. The mechanism of its action is seen in its influence on the chromosomes. – Other hormone‐like substances, the pheromones, are outstanding for their high activity; a few molecules are sufficient to trigger the characteristic behavioural response.
Fast Gas Reactions in Shock Waves and Detonations
Authors: Jost W. , Just T.
Published: December 2003

Shock waves provide a simple means of achieving high temperatures and hence of studying the kinetics of endothermal processes, e.g. dissociation reactions, above 100 °K. Detonations can also be used for this purpose, but are restricted to a few exothermal mixtures. The production and properties of shock waves and detonations and the most important analytical methods used for kinetic investigations are described, and some typical results are discussed.
Emulsion Polymerization of Vinyl Monomers under the Influence of Ionizing Radiation
Authors: Hummel D.
Published: December 2003

Ionizing radiation induces the polymerization of some vinyl monomers in aqueous emulsion with high radiation yields. With identical emulsion compositions, the kinetics of this reaction and the kinetics of emulsion polymerization induced by water‐soluble initiators are very similar. The rate of reaction in emulsion polymerization is about one hundred times greater than in bulk polymerization. The initiation of emulsion polymerization by means of ionizing radiation permits uniform “illumination” of the reacting volume, as well as almost any desired variation in the frequency of initiation during the reaction. The sharp decrease in the overall rate of reaction when initiation is interrupted during emulsion polymerization of styrene induced by γ‐rays contradicts the earlier concept of sharply separated reaction zones.
Principles and Techniques of Diffuse‐Reflectance Spectroscopy
Authors: Kortüm G. , Braun W. , Herzog G.
Published: December 2003

The prerequisites for applicability of the Kubelka‐Munk theory of diffuse reflectance for obtaining characteristic color curves of powders are discussed, and some experimental support for the theory is given. Methods are described for eliminating surface reflection, which is always superimposed upon the diffuse reflection and which therefore distorts the spectrum. The effect of interactions with the adsorbent on the reflection spectra of adsorbed molecules is demonstrated by means of examples, and the special suitability of the method for investigating chemisorption and for following reactions at phase boundaries is pointed out. By analogy to the Beer‐Lambert law, the Kubelka‐Munk function can be used for quantitative photometric analysis. The reflectance curves of white standards are presented, and measurements relating to the conditions for “infinitely thick layers” are reported. The scattering coefficient of the Kubelka‐Munk functions has been estimated for several samples of color‐filters as a functions of grain‐size and wavelength. The effect of moisture on diffuse reflectance spectra is discussed, and details of the measuring techniques are presented.
Formation and Cleavage of Dihydroxydiarylmethane Derivatives
Authors: Schnell H. , Krimm H.
Published: December 2003

Dihydroxydiarylmethane derivatives are formed by condensation of aromatic hydroxy and carbonyl compounds in the presence of acidic condensing agents at low temperatures or in the presence of bases at elevated temperatures. This article deals with formation and cleavage mechanisms in acid and basic media. As a result of the investigations reported, new methods of preparing unsymmetric dihydroxydiarylmethane derivatives and p‐alkenylphenols have been developed.
Production of Polyhydric Alcohols from Wood Polysaccharides
Authors: Sharkov V. I.
Published: December 2003

By hydrolysis and hydrogenolysis, plant polysaccharides, i.e. mainly cellulose and hemicelluloses, can be converted with high yields into polyhydric alcohols (hexitols, pentitols, glycerol, ethylene glycol, propylene glycol). Procedures which have been developed in the U.S.S.R. are described. Of particular interest is the simultaneous hydrolysis and hydrogenolysis of plant polysaccharides with noble metal catalysts. Here yields are almost quantitative.
Oligomers and Pleionomers of Synthetic Fiber‐Forming Polymers
Authors: Zahn H. , Gleitsman G. B.
Published: December 2003

The term “oligomer” is defined, and a survey of methods for the isolation and synthesis of cyclic and linear oligoesters, oligourethanes, oligo(acrylonitriles), and oligoamides is presented. The oligomers serve a valuable function as model substances for the investigation of many properties of the corresponding high polymers. This is shown using several examples (infrared spectroscopy, X‐ray spectroscopy, viscosity).
Permethylation of Oligomeric and Polymeric Carbohydrates and Quantitative Analysis of the Cleavage Products
Authors: Wallenfels K. , Bechtler G. , Kuhn Richard , Trischmann H. , Egge H.
Published: December 2003

Methylation of mono‐, oligo‐, and polysaccharides with methyl iodide/barium oxide or dimethyl sulfate/barium hydroxide in dimethyl sulfoxide as solvent rapidly leads to high degrees of methylation. Depending on the structure and solubility of the substrate, permethylation can be achieved either in one operation or by repetition of the same treatment. Procedures of permethylation of various carbohydrates are given. The methyl glycosides obtained on methanolysis can be separated and determined quantitatively by gas chromatography. The preparation of separating columns with minimum retention for this purpose is described. Pullulan was shown to have the structure of a completely linear polymer of maltotriose units connected by α‐1→6‐linkages. – In addition the gaschromatographic identification of methyl ethers of glucosamine and galactosamine is reported.
Preparation of N‐Alkoxyureas and Their Use as Selective Herbicides
Authors: Scherer O. , Hörlein G. , Härtel K.
Published: December 2003

N‐(4‐Chlorophenyl)‐N′‐methoxy‐N′‐methylurea (Aresin®)‐ and N‐(3,4‐dichlorophenyl)‐ N′‐ methoxy‐N′ ‐methylurea (Afalon®) are two new herbicides with characteristic selective activity. A simple and convenient method for their preparation is described.
Recent Developments in the Chemistry of Aminoboranes
Authors: Niedenzu K.
Published: December 2003

The isosterism of BN and CC grouping invites comparisons. Recent investigations on substituted aminoboranes R1R2NBR3R4 have been attempted in order to evaluate this concept of isosterism. Some of the latest results include evidence for geometric isomerism due to hindered rotation about the BN bond, isolation of isomeric compounds which can be considered as formal analogues of cyclohexanes, and the incorporation of BN groups into aromatic systems.
Equilibrium and Nonequilibrium in the Glycolysis System
Authors: Bücher Th. , Rüssmann W.
Published: December 2003

The relationship between the metabolic throughput within the network of energy‐furnishing metabolism and the deviation of its composite reacting units from equilibrium is discussed. Measurements have been made of the steady‐state relaxation times, and, following a suggestion by Alberty, their application is described. The results confirm and extend the concepts of intracellular redox relationships which the authors' research group outlined five years ago in this journal. The maximum difference between the redox potentials of the lactate/pyruvate and of the DPN/DPNH systems was calculated to be 2 mV. Deviations of the α‐glycerophosphate/dihydroxyacetone phosphate system measured in vivo are correlated with the rate of flow in the glycerophosphate cycle.
Amides of the Alkali and the Alkaline Earth Metals
Authors: Juza R.
Published: December 2003

Following preparative work, the behavior of amides towards excess ammonia (ammoniate formation) and on removal of ammonia (degradation to imides)was studied particularly with regard to the solid state (crystal structure) and the transition to the liquid phase (melting point). Energy relationships are discussed on the basis of enthalpies of formation. Studies on ternary amides and imides are still in the initial stage. – Emphasis is laid here on the establishment of parallels between amides and hydroxides as well as between the aquo and ammono systems, and also on the differences between the amides with their dipolar NH2‐ anion, and the halides. The results, although still incomplete, permit a survey to be given of experimental data with the aid of information obtained from the pertinent literature.
Intramolecular Free‐Radical Reactions
Authors: Heusler K. , Kalvoda J.
Published: December 2003

In the present article an attempt is made to summarize the steric requirements and the influence of neighboring groups which determine the course of intramolecular radical reactions. Steroids are used as substrates for these reactions, since here the spatial arrangement of the ring members and the distances between substituents are largely fixed. Furthermore, intramolecular free‐radical reactions are of practical importance in steroid chemistry in connection with substitution at non‐activated carbon atoms. Almost all the reactions discussed begin with the formation of an oxygen radical by oxidation of an alcohol with lead tetraacetate or by homolysis of the corresponding hypoiodite.
The Design of Phosphorylating Agents
Authors: Clark V. M. , Hutchinson D. W. , Kirby A. J. , Warren S. G.
Published: December 2003

Phosphorylating agents are compounds capable of transferring the group (HO)2P(O) in free or esterified form. Numerous phosphorylating agents can be classified into PXYZ systems, in which the element or group Z must be capable of accommodating the electrons of the PX bond. Systematic classification of PXYZ compounds and numerous examples of phosphorylation in chemistry and biochemistry are given.
Fundamental Aspects of Diffusion Processes
Authors: Jost W.
Published: December 2003

A simple description of diffusion processes and a derivation of the general laws of diffusion are given. The distribution with time of particles according to a random‐walk process is considered and compared with results derived from a differential equation. Diffusion coefficients for and examples of diffusion processes in various media (e.g. gases, solutions, solids, and high polymers) are given. “Uphill” diffusion, i.e. diffusion against the concentration gradient is also discussed. In addition, diffusion in anisotropic systems, in systems consisting of more than one phase and in multicomponent systems is treated.
Photochemical Substitutions on Metal Carbonyls and Their Derivatives
Authors: Strohmeier W.
Published: December 2003

The photochemical reaction of n‐ and π‐electron donors with metal carbonyls or their derivatives, which was discovered some years ago, provides a means of preparing a wide range of new metal‐carbonyl derivatives which are obtainable only in poor yields or not at all by thermal reactions. – Preparative methods are described. The mechanism of this photochemically induced substitution was elucidated for selected examples, and an attempt has been made to gain an insight into the polarity of the metal‐ligand bond. – This paper is intended as a survey of work published recently in this field.
Recoil Reactions of Tritium with Organic Compounds
Authors: Schmidt‐Bleek F. , Rowland F. S.
Published: December 2003

After “cooling”, the hot tritium atoms formed above thermal energies by nuclear reactions abstract or replace hydrogen atoms, and replace substituents X (e.g. alkyl, NH2, NO2, OH, COOH, F, Cl, Br, or I) in organic compounds. Isotope effects have been observed for protonated vs. deuterated compounds in several hot reactions. Models and mechanisms are discussed for the abstraction and replacement, for specific reactions on certain carbon atoms, and for the isotope effects. These are based on steric, bond‐energy, and kinetic considerations.
Structure and Crystallization Behavior of Glasses
Authors: Vogel W.
Published: December 2003

Almost all optical and technical glasses contain micro‐heterogeneities which can be seen using an electron microscope. These heterogeneous regions are shaped like small drops, and their size (20 to 500 Å) depends on the construction of the glass, on its temperature‐history, on the field strength of the cations, and also on the adjacent gas atmosphere. ‐ Preparation of valuable ultramicrocrystalline ceramics for industrial use from ordinary and photosensitive glasses involves controlled phase‐separation processes and subsequent crystallization.
Reactions of Metal Acetylacetonates
Authors: Collman J. P.
Published: December 2003

Certain metal acetylacetonates undergo reactions characteristic of aromatic systems. Outstanding among these are electrophilic substitutions and the formation of a stable diazonium fluoroborate. Unsymmetrically substituted chelates have been prepared by stepwise substitution of trifunctional complexes. Chemical and physical properties of such mixed‐ring complexes provide evidence for intramolecular interannular electronic effects transmitted through the metal ion.
The Chemistry of Diimine
Authors: Hünig S. , Müller H. R. , Thier W.
Published: December 2003

The presence of diimine in solution can be shown conclusively by the stereospecific cishydrogenation of symmetrical multiple bonds. Apart from reactions which have hitherto been attributed to hydrazine, this review deals primarily with the various sources and secondary reactions of diimine.
New Cotton Dyes
Authors: Hensel H. R. , Lützel G.
Published: December 2003

The present paper deals with new cotton dyes, approaching the subject from two directions. In the first section the synthesis of a new type of reactive dye from products of Peppeacetylene chemistry is reported. The second part describes a dyeing process which does not stat with reactive dyes. Instead, the homopolar bonding between dye and cotton is formed by linking the dye to the substrate via polyfunctional bridges. These two programs have led to the development of the ®Primazin P and ®Basazol dyes.
Relationships between Structures and Mass Spectra of Organic Compounds
Authors: Spiteller G. , Spiteller‐Friedmann Margot
Published: December 2003

Our knowledge concerning the relationships between the structure and mass spectra of organic compounds has widened immensely during the past few years. It has become possible to alter the course of fragmentation in the mass spectrometer by changing certain substituents using simple chemical reactions. The fragmentation products formed are then entirely different from those of the starting material. A combination of controlled mass‐spectrometric decomposition with chemical microreactions often permits the solution of complicated structural problems with a minimum expenditure of time and material. One example for the alteration of the fragmentation pattern by a simple chemical reaction is discussed in connection with the elucidation of the structure of pleiocarpamine.
Color and Constitution of Azo Compounds
Authors: Bock H. , Rudolph G. , Baltin E. , Kroner J.
Published: December 2003

Attempts to explain the surprising violet color of the new azobisphosphonic acid derivatives Y2OPNNPOY2 have led to the preparation and spectroscopic characterization of more than 60 azo compounds. The long‐wavelength n → π* transitions on which the color depends exhibit regularities which justify the assumption of substitutent‐specific absorption increments. The complex relation between color and constitution of azo compounds can be qualitatively explained with the aid of orbital models. Infrared and ultraviolet spectral data show that conjugation is inhibited by tetra‐coordinated phosphorus (V). the π‐system of these compounds therfore comprises only for atoms, P·N·N·P. The unexpected violet color of the phosphorus azo compounds can be ascribed to a π*/d orbital interaction. The substituent effects described have general significance, and n→π*transitions of other chromophores are similarly affected.
Automation of X‐Ray Structural Analysis Part I. Automation of the Measuring Process
Authors: Hoppe W.
Published: December 2003

The present paper is the first of two reports describing the principles which can be applied to the construction of automatic counter‐tube diffractometers for the X‐ray analysis of crystals. These instruments can reduce the time required for the analysis of an organic crystal (measurement of a few thousand intensities) from several months (by the photographic method) to a few days.
A Code for the Classification of the Ultraviolet Spectra of Organic Compounds
Authors: Pestemer M. , Bergmann G. , Perkampus H.‐H. , Schrader B.
Published: December 2003

The ultraviolet spectra of all organic compounds can be classified according to the chemical constitution with the aid of a simple code based on a ten‐digit decimal system, each digit indicating the “spectroscopic weight” of the encoded information. The code discussed here will shortly be used in the Atlas of Ultraviolet Spectra which appears in the Documentation of Molecular Spectroscopy Series.
Fluorosulfuric Acid as a Reaction Medium and Fluorinating Agent in Inorganic Chemistry
Authors: Engelbrecht A.
Published: December 2003

Fluorosulfuric acid is known both in aqueous solution and as the anhydrous compound. The anhydrous acid exhibits electrical conductivity which indicates its autodissociation. Even strong acids such as H2SO4 or HCIO4 behave as proton acceptors, i.e. as bases, in fluorosulfuric acid. Volatile inorganic acid fluorides can be readily prepared using fluorosulfuric acid as fluorinating agent.
Progress in the Chemistry and Molecular Biology of Flavins and Flavocoenzymes
Authors: Hemmerich P. , Veeger C. , Wood H. C. S.
Published: December 2003

An attempt is made to create a basis for the understanding of flavin‐ (Vitamin B2‐) dependent oxidations in terms of molecular structure. The main points of this survey can be summarized as follows: (a) The flavins must be differentiated according to their redox states (quinone state, radical state, hydroquinone state), since configuration, energy content of the tautomeric forms, metal affinity etc., alter drastically during reduction. – (b) The methyl group on C‐8 of the flavoquinone is reactive. – (c) The electron transfer properties of the flavin system frequently depend on the coupling of secondary redox systems to the apoprotein. This interaction thermodynamically stabilizes the half‐reduced state of the flavin. – (d) Numerous novel flavin types, among them stabilized free radicals, have become available through syntheses at the dihydro stage. – (e) Reaction of the flavin radical with O2 is slow as long as no disproportionation occurs, i.e. the fast flavin autoxidation proceeds via the dihydro state. – (f) The flavin nucleus gains affinity for heavy metal ions only by the acceptance of one, and only one, electron. – (g) Redox activity and contact with the flavin coenzyme have been confirmed for Fe and Mo, which occur in flavoproteins. The properties of the metal coordination sphere are determined primarily by sulfur‐containing groups of the apoprotein.
1,2‐Dehydrobenzene
Authors: Wittig G.
Published: December 2003

The historical development of the methods to generate dehydrobenzene is outlined. Dehydrobenzene readily adds nucleophilic as well as electrophilic partners. Diels‐Alder addition to dienes is moreover a valuable synthetic principle. The intermediacy of dehydrobenzene has been proved for polar additions by labeling with 14C or with a substituent. The same conclusion has been reached in Diels‐Alder additions by competition experiments. The considerable selectivity displayed by dehydrobenzene in both types of reaction is not caused by solvation, since recently the existence of dehydrobenzene in the gas phase has been established, where it reacts similarly as in solution.
Progress in Optical Circular Dichroism
Authors: Velluz L. , Legrand M.
Published: December 2003

An apparatus first described in 1961 for the measurement of circular dichroism down to 220 mμ has been improved and its range extended down to 185 mμ. Some examples are given in the field of dienes, conjugated ketones, and aromatic chromophores. A more extensive study of protein structures was developed with the following results: (a) helical polypeptides show a complex dichroism in the far ultraviolet with three components (192 mμ, 204 mμ, 225 mμ), characteristic of the helical array of peptide groups; (b) human serum albumin shows a very similar curve of dichroism and is 60% helical; (c) urea denaturation, as judged by dichroism, is a reversible phenomenon; (d) a solvent such as chloroethanol increases the helical content of human serum albumin and clupein and has only a very small action on poly‐L‐glutamic acid; (e) the rupture of SS bonds in human serum albumin favors the attack of denaturing agents such as urea; (f) detergents help to maintain the rigid structure of human serum albumin after the rupture of SS bonds.
The Alkylating Properties of Alkyl Thiophosphates
Authors: Hilgetag G. , Teichmann H.
Published: December 2003

Thiophosphate and phosphate esters have been synthesized in great variety since about 1945, and are being produced in increasing quantities, mainly for plant protection. An important property of alkyl phosphates and thiophosphates is their alkylating power, which is comparable with that of dialkyl sulfates and alkyl p‐toluenesulfonates. The chemistry of thiophosphates is largely determined by their alkylating properties, since the sulfur, both in the alkyl thiophosphate and in the thiophosphate anion formed on dealkylation, can act as a point of attack for self‐alkylation.
The Modifications of Niobium Pentoxide
Authors: Schäfer Harald , Gruehn R. , Schulte F.
Published: December 2003

Niobium pentoxide crystallizes in numerous modifications. The present paper describes their mode of formation, structures, and thermal properties.
Madelung Constants
Authors: Hoppe R.
Published: December 2003

Madelung constants are simple numbers which depend on the type of structure investigated. They are needed for the calculation (using the Born‐Haber cycle) of lattice energies and enthalpies of formation of ionic compounds. Each Madelung constant is the sum of partial Madelung constants which represent the contributions of the individual ions to the total lattice energy. The partial Madelung constants depend on the ionic charge and, clearly though not stringently, on the coordination number. On the other hand, each Madelung constant can be represented by a sum of Madelung constants for related simple primitive AB structures. Surprisingly, these Madelung constants are numerically interrelated in a simple manner, and are related to the partial Madelung constants of interstitial sites. – Madelung constants of parameter‐dependent structures (e.g. of the rutile or anatase type) and their variations with the structure‐determining quantities are of particular interest. Madelung constants also yield information in the case of complex compounds and – surprisingly – of non‐metal compounds (e.g. XeF2, XeF4, XeF2·XeF4).
Allyl‐Transition Metal Systems
Authors: Wilke G. , Bogdanović B. , Hardt P. , Heimbach P. , Keim W. , Kröner M. , Oberkirch W. , Tanaka K. , Steinrücke E. , Walter D. , Zimmermann H.
Published: December 2003

As a continuation of a report published in 1963, recent results in the field of allyl‐transition metal complexes are described

The term “allyl compounds” in the present paper refers not only to compounds containing the simple allyl group (CH2CHCH2), but also to those that contain substituted allyl groups or allyl groups forming part of a ring system.

. Syntheses and reactions of these compounds, as well as the bonding between metal and allyl group, are discussed. Allyl‐transition metal complexes form the basis of extremely selective catalysts for homogeneous reactions of 1, 3‐diolefins and of olefins; the metal atoms in these “matrix” catalysts are either “bare”

The description “bare” is applied to complexed metal atoms from which the ligands can be quantitatively displaced by the substances taking part in catalytic reactions.

or are bound to only a few ligands.