Showing papers by "University of Würzburg published in 1982"

Basic Principles of the CIP-System and Proposals for a Revision†

Abstract: “From Configurational Notation of Stereoisomers to the Conceptual Basis of Stereochemistry” is the title of a lecture [V. Prelog, ACS Symp. Ser. No. 12 (1975) 179] in which the chronologically and alphabetically third member of the CIP-triumvirate discusses the history of the CIP-system. The experience accumulated in the meantime, particularly the efforts to teach computers to use the system as described in 1966 by Cahn, Ingold and Prelog, has shown that certain of its aspects must be more strictly formulated and others modified. Questions dealing with stereoisomers (and stereotopicity), which previously have been treated predominantly in a pragmatic manner, are now discussed in a systematic way.

Dependence of the life span of the honeybee ( Apis mellifica ) upon flight performance and energy consumption

Abstract: The life span of worker-honeybees is determined by the duration of the hive-period and of the foraging period (Figs. 1,2). The duration of the forgaing period is regulated in the following way: Total flight performance of the individual bee seems to be fixed. Daily flight performance strongly affects total flight duration. High daily flight performance decreases maximal flight duration and vice versa. Foragers accumulate the highest glycogen reserves in the flight muscles compared to other stages (Figs. 3, 4). They use these reserves to overcome starvation or when growing old. Young foragers are able to restore glycogen reserves after sugar intake, whereas old foragers were found to have a reduced glycogen synthesizing ability (Fig. 5). The results indicate that bees exhaust their energysupplying mechanisms after a definite total flight performance.

The nonlinear programming method of Wilson, Han, and Powell with an augmented Lagrangian type line search function

Abstract: The paper represents an outcome of an extensive comparative study of nonlinear optimization algorithms. This study indicates that quadratic approximation methods which are characterized by solving a sequence of quadratic subproblems recursively, belong to the most efficient and reliable nonlinear programming algorithms available at present. The purpose of this paper is to analyse the theoretical convergence properties and to investigate the numerical performance in more detail. In Part 1, the exactL 1-penalty function of Han and Powell is replaced by a differentiable augmented Lagrange function for the line search computation to the able to prove the global convergence and to show that the steplength one is chosen in the neighbourhood of a solution. In Part 2, the quadratic subproblem is exchanged by a linear least squares problem to improve the efficiency, and to test the dependence of the performance from different solution methods for the quadratic or least squares subproblems.

Glutathione reductase from human erythrocytes. The sequences of the NADPH domain and of the interface domain.

Abstract: 1. Sequence analysis of the NADPH domain (residues 158--293) and of the interface domain (365--478) was based on 12 CNBr fragments, which were isolated using ion-exchange chromatography and paper methods. Fragments with more than 15 residues were digested further with trypsin and chymotrypsin. The isolated peptides were sequenced by automated solid-phase Edman degradation. All sequenced peptides were ordered and overlapped by computerized comparisons with a complete sequence guessed from the electron density map of the protein. In the case of short CNBr fragments, this alignment was confirmed by the sequence analysis of protein fragments resulting from incomplete CNBr cleavage. 2. In the NADPH domain, residue 197, which is involved in an induced-fit mechanism, was identified as a tyrosine. The structure of the NADPH domain is probably homologous with the NAD domain of lipoamide dehydrogenase and with the FAD domain of several proteins, but not with NADPH domains of known chain-fold in other proteins. 3. The paper completes the sequence analysis of glutathione reductase so that the enzyme is now known in atomic detail. The numbering scheme of the chemically determined sequence will be used henceforth in crystallographic studies also. As inferred from the sequence data each of the two identical chains contains 478 amino acid residues, the composition being Cys10, Asp21, Asn17, Thr31, Ser31, Glu29, Gln11, Pro24, Gly43, Ala42, Val44, Met15, Ile29, Leu34, Tyr13, Phe14, Lys34, His16. Arg17, and Trp3. From these data an Mr of 2 x 51 600 was calculated for the FAD-free apoenzyme and an Mr of 2 x 42 400 for the holoenzyme.

On the Convergence of a Sequential Quadratic Programming Method with an Augmented Lagrangian Line Search Functions.

Abstract: Sequential quadratic programming methods as developed by Wilson, Han, and Powell have gained considerable attention in the last few years mainly because of their outstanding numerical performance. Although the theoretical convergence aspects of this method and its various modifications have been investigated in the literature, there still remain some open questions which will be treated in this paper. The convergence theory to be presented, takes into account the additional variable introduced in the quadratic programming subproblem to avoid inconsistency, the one-dimensional minimization procedure, and, in particular, an “ active set” strategy to avoid the recalculation of unnecessary gradients. This paper also contains a detailed mathematical description of a nonlinear programming algorithm which has been implemented by the author. the usage of the code and detailed numerical test results are presented in [5].

The Dirac-Kahler Equation and Fermions on the Lattice

Abstract: The geometrical description of spinor fields by E. Kahler is used to formulate a consistent lattice approximation of fermions. The relation to free simple Dirac fields as well as to Susskind's description of lattice fermions is clarified. The first steps towards a quantized interacting theory are given. The correspondence between the calculus of differential forms and concepts of algebraic topology is shown to be a useful method for a completely analogous treatment of the problems in the continuum and on the lattice.

Nucleotide Sequence and Secondary Structure of Citrus Exocortis and Chrysanthemum Stunt Viroid

Abstract: The complete nucleotide sequence of citrus exocortis viroid (CEV, propagated in Gymura) and chrysanthemum stunt viroid (CSV, propagated in Cineraria) has been established, using labelling in vitro and direct RNA sequencing methods and a new screening procedure for the rapid selection of suitable RNA fragments from limited digests. The covalently closed circular single-stranded viroid RNAs consist of 371 (CEV) and 354 (CSV) nucleotides, respectively. As previously shown for potato spindle tuber viroid (PSTV, 359 nucleotides), CEV and CSV also contain a long polypurine sequence. Maximal base-pairing of the established CEV and CSV sequences results in an extended rod-like secondary structure similar to that previously established for PSTV and as predicted from detailed physicochemical studies of all these viroids. Although the three viroid species sequenced to date differ in size and nucleotide sequence, there is 60--73% homology between them. As PSTV, CEV and CSV also contain conserved complementary sequences which are separated from each other in the native secondary structure. We postulate that the resulting 'secondary' hairpins, being formed and observed in vitro during the complex process of thermal denaturation of viroid RNA, must have a vital, although yet unknown, function in vivo. The possible origin and function of viroids are discussed on the basis of the characteristic structural features and of a considerable homology with U1a RNA found for a region highly conserved in the three viroids.

Ribosomal RNA transcription in vitro is species specific

Abstract: Eukaryotic cells possess three distinct nuclear DNA-dependent RNA polymerases which are responsible for transcription of different sets of genes (for review see refs 1, 2). Recently, cell-free transcription systems have been developed which faithfully initiate transcription of isolated genes by the corresponding RNA polymerase in the presence of crude cellular extracts. These cellular extracts supply additional components required for specific transcription3–6. Successful in vitro systems for transcription of RNA polymerase II or III genes were developed using either heterologous or homologous components7–11. In contrast, an analogous cell-free system for the RNA polymerase I transcription unit from mouse has been shown to be active only with homologous extracts from mouse cells6. Data presented here show that in vitro transcription of ribosomal DNA isolated from mouse, human and a protozoan requires completely homologous components. None of the three active cell-free systems is capable of correct initiation on the nonhomologous templates. Further, supplementation of mouse extracts with purified protozoan RNA polymerase I failed to result in specific transcription of the protozoan rDNA, suggesting that the species specificity of pre-ribosomal RNA synthesis resides, in part, in the transcription factors.

Morphological and biochemical heterogeneity of amniotic fluid cells in culture.

Abstract: Publisher Summary This chapter describes the morphological and biochemical heterogeneity of amniotic fluid cells in culture. Midgestation amniotic fluid cells constitute a precious source of human cells for the purpose of cell biological investigation. Several properties contribute to the diagnostic and scientific value of these cells, the most important of which are the presence in a single amniotic fluid specimen of multiple, morphologically and biochemically distinct cell types that are all derived from the fetus or from fetal membranes and thus are isogenic. It is found that in addition to variable amounts of cellular debris and anucleate particles, second-trimester amniotic fluid contains between 103 and 105 nucleated cells per milliliter of fluid. All epithelial surfaces in direct or indirect contact with the amniotic cavity are possible sites of origin of these cells. According to their behavior in the culture environment, nucleated amniotic fluid cells can be operationally divided into three separate categories. The first category includes cells that remain afloat even after prolonged periods of incubation. It is found that amniotic fluid F-type cells have the greatest in vitro growth potential of all colony-forming cells.

Mutagenic properties of allylic and alpha, beta-unsaturated compounds: consideration of alkylating mechanisms.

Abstract: 1. Allyl and allylic compounds may exert alkylating activities by SN1, SN2 and SN2' mechanisms. This direct alkylating potential can be determined quantitatively by a modified 4-NBP (4-nitrobenzyl pyridine) test. 2. The alkylating activities in a systematically selected series of allyl and allylic compounds correlate well with the direct mutagenic potential as determined in the Ames test using Salmonella typhimurium TA 100 as tester strain. 3. The allylic structure is a prerequisite for these types of activities since structurally related molecules lacking the allylic moiety are inactive in this respect. 4. The potency of both the alkylating and mutagenic activity is determined by the strength of the leaving group: --OSO2CH3 greater than I greater than Br greater than Cl greater than--NCS. 5. Indirect mutagenicity, through metabolic activation of the olefinic bond (by addition of S9 mix to the tester medium), can be ruled out for practically all compounds, the only exception found being 2,3-dichloro-1-propene where an increase of mutagenicity is encountered after addition of S9 mix; mechanistic explanations for this exception are provided. 6. Analogous activation is demonstrated for benzyl halides, the alkylating potency of which is even higher than that of genuine allylic compounds. 7. A variety of methyl- and chlorine-substituted allyl compounds has been included in the study: both groups increase activity, either by +I (CH3) or by +M effects (Cl). 8. alpha, beta-Unsaturated carbonyl compounds, e.g. acrolein and crotonaldehyde, also display direct mutagenic activity which is due to a completely different mechanism: covalent binding to nucleophilic sites of DNA bases by Michael addition. Methyl and other alkyl substitutions decrease the mutagenic potential in this type of compound. The corresponding alcohols, also displaying mutagenic activity but to a lesser degree, are metabolically activated by ADH (alcohol dehydrogenase) of the tester strain microbes to the aldehydes or ketones.

Correlation between changes in photosynthetic activity and changes in total protoplast volume in leaf tissue from hygro-, meso- and xerophytes under osmotic stress.

Abstract: Rates of photosynthesis of leaf slices from various hygro-, meso- and xerophytes were measured in the absence of stomatal control in various stages of osmotic dehydration The external osmotic potential π° for a 50% inhibition of photosynthesis varied between 20 bar in some hygrophytes up to 50 bar in xerophytes The response of photosynthetic enzymes to increased salt concentrations in the reaction medium was similar in leaf extracts from hygro-, meso- and xerophytes The total protoplast volume in vacuum-infiltrated leaf discs from various plants was measured as the difference between 3H2O-labeled space and [14C]sorbitol-labeled space In all plants, the protoplast volume could be reduced to about 55% of the maximum volume of tissue in equilibrium with water, without decreasing photosynthesis Reduction of the maximal protoplast volume below 55% decreased photosynthesis in all tissues to the same decreased photosynthesis in all tissues to the same degree At 20% maximal volume, photosynthesis of all plants was completely inhibited The differential decrease of protoplast volumes of various leaf tissues in response to changes in π° was mainly due to the different osmotic potential of the cell sap (πcs) The relative contribution of sugars to the overall osmolarity of the cell sap was up to nineteen times higher in xerophytes than in hygrophytes Short-term recovery of photosynthesis after hypertonic stress was good in xerophytes, incomplete in mesophytes and absent in hygrophytes There was also a large discrepancy between the partial recovery of protoplast volumes and the complete absence of a recovery of photosynthesis in hygrophytes

A portable steady-state porometer for measuring the carbon dioxide and water vapour exchanges of leaves under natural conditions.

Abstract: A portable porometer is described for measuring the steady-state CO2 and H2O exchange rates of leaves under natural conditions. The porometer has an open gas exchange system which monitors the differences in concentrations of CO2 and H2O entering and leaving a cuvette which is clamped on or around leaves. The cuvette is designed to maintain ambient air temperature and humidity around the leaf. This instrument may also be used to determine CO2 response curves in the field. Examples of diurnal courses are presented for attached leaves of different species having high and low rates of CO2 exchange.

Structure-mutagenicity relationship in α,β-unsaturated carbonylic compounds and their corresponding allylic alcohols

Abstract: Several α,β-unsaturated carbonylic compounds and their corresponding allylic alcohols were tested in a modified Salmonella typhimurium mutagenicity assay according to Rannug et al. (1976) with and without metabolic activation by S9 mix. The mutagenic activities of the test substances were correlated with their chemical structures. Allyl alcohol exerted a significant direct mutagenic activity despite its lack of a good leaving (750 revertants/μmole). Glycidol, the epoxide of allyl alcohol, showed a lower direct mutagenic potential (80 revertants/μmole), whereas the corresponding aldehyde, acrolein, exhibited a direct mutagenicity 3 times higher than that of allyl alcohol. The possibility of an oxidation of allyl alcohol to its corresponding α,β-unsaturated carbonyl compound, acrolein, by bacterial alcohol dehydrogenase is discussed. The 3 methyl-substituted homologues of allyl alcohol, crotyl alcohol, 2-methallyl alcohol and 3-buten-2-ol, only showed borderline mutagenicity, while the higher homologs, 2-cyclohexen-1-ol, cinnamyl alcohol, geraniol and linalood, did not show any mutagenic properties. In contrasst with the methyl-substituted homologs of allyl alcohol, the methylated homologs of acrolein, croton aldehyde, 2-methylacrolein and methylvinyl ketone, were clearly mutagenic. Of the higher α,β-unsaturated carbonyl compounds tested in this study, only 2-cyclohexen-1-one, which has the lowest molecular weight, exerted a very small direct mutagenic effect, whereas cinnamylaldehyde and citral did not show any mutagenicity. The addition of S9 mix invariably led to a decrease in mutagenicity; this is most distinct with those compounds that had the highest direct mutagenic potential. The chemical reactivity of acrolein with deoxyadenosine was confirmed in an experiment in vitro.

Failure of killed Listeria monocytogenes vaccine to produce protective immunity.

Abstract: We report here experiments which, in contrast to recently published data1,2, suggest that protection against lethal doses of viable Listeria monocytogenes cannot be achieved by previous injection with killed Listeria vaccine neither by adding macrophage-blocking agents such as dextran sulphate nor by using C3H/HeJ mice having inborn macrophage defects. This discrepancy can be explained by the ineffective killing of bacteria at 56 °C, resulting in injection of small numbers of viable bacteria; such doses are normally subinfective and do not provide immunity. Blocking of the macrophage system by dextran sulphate3, however, or use of C3H/HeJ mice with inborn macrophage defects4 renders these doses fully infective, hence providing subsequent protective immunity5.

Space-Times Admitting Killing-Yano Tensors. II

Abstract: In this paper we derive canonical line elements admitting a simple KillingYano tensor f* ab. There exist three distinct cases according to the character o f f* ab (spacelike, timelike, null). We reveal several close analogies between the vector field la = f * arp r along a geodesic with tangent field p r and the angular momentum l = rxpin the case of a spacelike Killing-Yano tensor. In particular, we show that, in consequence of the Killing-Yano tensor equations, there exists an analogue of the three-dimensional position vector field in certain hypersurfaces and th at la can be written in the form (r x p )a. Furthermore, an analogue of the ‘ equatorial plane ’ of the classical Kepler problem can be constructed intrinsically.

The control by atmospheric factors and water stress of midday stomatal closure in Arbutus unedo growing in a natural macchia.

Abstract: Midday closure of stomata of well-watered (ψ between-10 and-25 bar) or moderately stressed (ψ between-25 and-35 bar) Arbutus unedo plants occurs when midday leaf temperatures increase above 30°C and vapor pressure difference between leaf air spaces and the external air increases above approximately 30 mbar/bar. Moderate water stress decreases maximum conductance and may result in greater sensitivity to high leaf temperature and vapor pressure dificit, which results in earlier closure and later reopening of stomata. Severe water stress (ψ of-50 bar) changes the form of the daily pattern observed for leaf conductance. A single morning peak in conductance occurs followed by decrease in conductance over the remainder of the day. Morning fog in Portugal during the dry season may facilitate stomatal opening and may allow improvement of carbon balances of the leaves for short periods, but contributes little to improvement of plant water balances over the longer term.

Aromaten(phosphan)metall‐Komplexe, I. Die Vorstufen zur Synthese der Metall‐Basen ArM(PR3)2 und ArM(PR3)L (M = Ru, Os)

Abstract: Die halogen-verbruckten Verbindungen [ArRuX2]2 (AR = C6H6, p-Cymol, C6Me6; X = Cl, und AR = C6H6; X = I) und [C6H6OsI2]2 reagieren mit Lewis-Basen L wie z. B. CO, tertiaren Phosphanen oder Trimethylphosphit zu den einkernigen Komplexen ArMX2(L) (1 – 9). Aus diesen erhalt man (fur AR = C6H6) mit AgPF6 in Aceton (ac) die Verbindungen [C6H6RuCl(L)(ac)]PF6 (10 – 12) und [(C6H6ML)2(μ-X)2(PF6)2](C6H6ML)[2(μ-X)2](PF6) 2 (13 – 20). Bei der Reaktion von [ArRuX2]2 und [C6H6OsI2]2 mit einem Uberschus an PR3 und NH4PF6 in Methanol entstehen die Komplexe [ArMX(PR3)2]PF6 (21 – 29). Die Synthese der analogen Verbindungen [ArMX(PR3)L]PF6 (30 – 39) gelingt durch Umsetzung von ArMX2(L) mit PR3 und NH4PF6 in Methanol. Die Osmium-Komplexe [C6H6OsI(L)2]PF6 (40, 41) und [C6H6OsI(PR3)CO]PF6 (42, 43) werden aus [(C6H6OsL)2(μ-I)2(PF6)2] und L bzw. aus C6H6OsI2(PR3) und CO in Gegenwart von AgPF6 dargestellt. Arene(phosphane)metal Complexes, I The Precursors for the Synthesis of the Metal Bases ArM(PR3)2 and ArM(PR3)L (M = Ru, Os) The halide-bridged compounds [ArRuX2]2 (AR = C6H6, p-cymene, C6Me6; X = Cl, and AR = C6H6; X = I) and [C6H6OsI2]2 react with Lewis bases L, e. g. Co, tertiary phosphanes, or trimethyl phosphite, to give the mononuclear complexes ArMX2(L) (1 – 9). From these (AR = C6H6) and AgPF6 in acetone (ac) the compounds [C6H6RuCl(L)(ac)]PF6 (10 – 12) and [(C6H6ML)2(μ-X)2](PF6) 2 (13 – 20) are obtained. Reaction of [ArRuX2]2 and [C6H6OsI2]2 with an excess of PR3 and NH4PF6 in methanol yields the complexes [ArMX(PR3)2]PF6 (21 – 29). The synthesis of the analogous compounds [ArMX(PR3)L]PF6 (30 – 36) is achieved by the reaction of ArMX2(L) with PR3 and NH4PF6 in methanol. The osmium complexes [C6H6OsI(L)2]PF6 (40, 41) and [C6H6OsI(PR3)CO]PF6 (42, 43) are prepared from [(C6H6OsL)2(μ-I)2](PF6) 2 and L or from C6H6OsI2(PR3) and CO in the presence of AgPF6, respectively.