Artificial Light Regulation of an Allosteric Bienzyme Complex by a Photosensitive Ligand

The artificial regulation of proteins by light is an emerging subdiscipline of synthetic biology. Here, we used this concept to photocontrol both catalysis and allostery within the heterodimeric enzyme complex imidazole glycerol phosphate synthase (ImGP‐S). ImGP‐S consists of the cyclase subunit HisF and the glutaminase subunit HisH, which is allosterically stimulated by substrate binding to HisF. We show that a light‐sensitive diarylethene (1,2‐dithienylethene, DTE)‐based competitive inhibitor in its ring‐open state binds with low micromolar affinity to the cyclase subunit and displaces its substrate from the active site. As a consequence, catalysis by HisF and allosteric stimulation of HisH are impaired. Following UV‐light irradiation, the DTE ligand adopts its ring‐closed state and loses affinity for HisF, restoring activity and allostery. Our approach allows for the switching of ImGP‐S activity and allostery during catalysis and appears to be generally applicable for the light regulation of other multienzyme complexes.     

The diastereofacial selectivity of the addition of various 1-metalated 1-heptynes to substituted cyclopentanecarbaldehydes. – The use of 1-titanated 1-heptyne for the construction of the alkyl side chain of Prostaglandins

A highly diastereoselective addition of 1-heptyne to substituted cyclopentanecarbaldehydes is one of the indispensable prerequisites to the construction of the (S)-3-hydroxy-1(E)-octenyl side chain of prostaglandins by palladium(II)-catalyzed [3,3]-sigmatropic rearrangement of allylic acetates. It was found that 1-titanated 1-heptynes afford the Cram product at best with a diastereofacial selectivity of 92.5%. The corresponding lithium and magnesium compounds are less diastereoselective.     

Continuous Application of Polyglycerol‐Supported Salen in a Membrane Reactor: Asymmetric Epoxidation of 6‐Cyano‐2,2‐dimethylchromene

In the current work, suitability of hyperbranched polyglycerol as a high loading catalyst support is demonstrated. A polyglycerol‐supported manganese‐salen complex (chemzyme) is applied as a homogeneous catalyst in the epoxidation of 6‐cyano‐2,2‐dimethylchromene. The recyclability of the corresponding catalyst was investigated in repetitive batch experiments as well as a continuous operation of the reaction in an ultrafiltration membrane reactor. An enhanced stability of the catalyst in repetitive batches was observed as a result of immobilization whereby the total turnover number increased from 23 in a single batch to 80 in four repetitive batches. To enable continuous operation, a continuously operated, stirred tanked reactor (CSTR) was equipped with an ultrafiltration membrane (MPF‐50) and a retention of 98% was determined. The continuous chemzyme membrane reactor was operated over the course of 20 residence times. After approximately 12 residence times, the steady state was reached yielding 70% conversion as well as an enantiomeric excess up to 92%. A space‐time yield (sty) of 458 g L ⁻¹ d⁻¹ and a turnover frequency (TOF_reaction) of up to 18 h⁻¹ was reached in the steady state. It was determined that the total turnover number (TTN) was enhanced by a factor of 10 from 24 (batch) up to 240 for 20 residence times in CSTR operation.     

PEAK-INSENSITIVE NON-PARAMETRIC SPECTRUM ESTIMATION

Abstract. We study the problem of non-parametric spectrum estimation of a stationary time series that might contain periodic components. In this case the periodogram ordinates have a significant amplitude at frequencies near the frequencies of the periodic components. These can be regarded as outliers in an asymptotically exponential sample. We develop a non-parametric estimator for the spectral density that is insensitive to these outliers in the frequency domain. This is done by robustifying the usual kernel estimator (smoothed periodogram) by means of M-estimation in the frequency domain. We propose to use data-tapered periodograms, which yield a drastic improvement of the procedure, typically for the contaminated situation. This is both shown theoretically and supported by means of simulation. We show consistency of the resulting estimator in the general case, and asymptotic normality in the special case of a Gaussian time series, whether contamination is present or not. Finally we illustrate the finite sample performance of the estimating procedure by some simulation results and by application to the Canadian lynx trappings data.     

Patent families as macro level patent value indicators: applying weights to account for market differences

This paper introduces a methodology for the construction of a country level patent value indicator based on the family size of a country’s patent profile at the level of technology fields. Because individual family members target different markets and technologies have a different propensity to internationalization, family size has been shown to have a restricted power to assess the quality of patent profiles of countries. We address this gap by weighting the members of patent families filed at different patent offices before calculating the family size indicators, to account for the market potential in which the patents of these families were filed. We apply different weighting schemes and test which scheme is best able to explain the export performance of countries. In order to conduct our analyses, a panel dataset, consisting of annual data (1990–2002) on international trade from the UN-COMTRADE database and patent data from the “EPO Worldwide Patent Statistical Database” (PATSTAT), was compiled. Several bivariate analyses reveal that weighted and unweighted family counts are highly correlated, meaning that statistics based on absolute (weighted or unweighted) family counts are barely affected by the chosen weighting factor. This, however, is different when using the average family size, where weighting the family members by imports, as well as GDP, can be shown to have a robust positive effect to explaining export performance. The imports and the GDP weighted average family size are thus able to act as a consistent indicator of patent value at the country and technology field level.     

INDUCTIVE LEARNING FOR PARAMETER OPTIMIZATION

Optimization of simulation model output is one of the most important tasks in a simulation study of a complex system. Efficacy of an optimization approach is expressed in the accuracy of locating a global extremum, as well as in the number of investigated search points. The approach Machine Learning Optimization (ML-Opt), presented in this article, explores functional dependencies between search points in order to reduce the number of evaluations. Functional relations between search points are determined by an inductive learning algorithm, which generates a classifier used as a control structure in the optimization process. The classifier approximates the structure of the unknown goal function given by a simulation model and affects the generation of new search points. A discussion of a numerical example concludes the paper.     

Beiträge des WBW zur Entwicklung der Logistik in Forschung und Lehre

On the occasion of the 50th anniversary, the contributions of the Department of Economic and Management Sciences (WBW), University of Leoben, to the development of logistics in research and education are highlighted. After a discussion of the milestones of logistics and related dissertations of the department WBW, the newly resulting curriculum is presented. The paper concludes with an outlook on a possible new research topic.     

Paying to belong: When does rejection trigger ingratiation?

Societies and social scientists have long held the belief that exclusion induces ingratiation and conformity, an idea in contradiction to robust empirical evidence linking rejection with hostility and aggression. The classic literatures on ingratiation and conformity help resolve this contradiction by identifying circumstances under which rejection may trigger efforts to ingratiate. Jointly, findings from these literatures suggest that when people are given an opportunity to impress their rejecters, ingratiation is likely after rejection experiences that are harsh and that occur in important situations that threaten the individual's self-definition. Four studies tested the hypothesis that people high in rejection sensitivity and therefore dispositionally concerned about rejection will utilize opportunities to ingratiate after harsh rejection in situations that are self-defining. In 3 studies of situations that are particularly self-defining for men, rejection predicted ingratiation among men (but not women) who were high in rejection sensitivity. In a 4th study, harsh rejection in a situation particularly self-defining for women predicted ingratiation among highly rejection-sensitive women (but not men). These findings help identify the specific circumstances under which people are willing to act in socially desirable ways toward those who have rejected them harshly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Iterated Weakest Link

We outline a model for security investment that reflects dynamic interaction between a defender, who faces uncertainty, and an attacker, who repeatedly targets the weakest link. Using the model, we derive and compare optimal security investment over multiple periods, exploring the delicate balance between proactive and reactive security investment.