Comparative Genomics and Evolution of Molybdenum Utilization

The trace element molybdenum (Mo) is the catalytic component of important enzymes involved in global nitrogen, sulfur, and carbon metabolism in both prokaryotes and eukaryotes. With the exception of nitrogenase, Mo is complexed by a pterin compound thus forming the biologically active molybdenum cofactor (Moco) at the catalytic sites of molybdoenzymes. The physiological roles and biochemical functions of many molybdoenzymes have been characterized. However, our understanding of the occurrence and evolution of Mo utilization is limited. This article focuses on recent advances in comparative genomics of Mo utilization in the three domains of life. We begin with a brief introduction of Mo transport systems, the Moco biosynthesis pathway, the role of posttranslational modifications, and enzymes that utilize Mo. Then, we proceed to recent computational and comparative genomics studies of Mo utilization, including a discussion on novel Moco-binding proteins that contain the C-terminal domain of the Moco sulfurase and that are suggested to represent a new family of molybdoenzymes. As most molybdoenzymes need additional cofactors for their catalytic activity, we also discuss interactions between Mo metabolism and other trace elements and finish with an analysis of factors that may influence evolution of Mo utilization.     

Triads

Triads are four-termed complexes with end terms connected by a translation functor, similar to triangles in a triangular category. We use triads to give an adequate theory of L-functors, introduced in [W. Rump, The category of lattices over a lattice-finite ring, Algebras and Representation Theory, in press] to investigate the global structure of categories with almost split sequences. Roughly speaking, L-functors extend the Auslander–Reiten translate to morphisms and thereby make it functorial.     

Phase preparation in steady-state free precession MR elastography

Strain and motion measurements in balanced steady-state free precession (bSSFP) imaging require high magnetic field homogeneity. This requirement is due to the nonlinear signal response to spin phase variations in bSSFP. Here, a technique that utilizes background gradients for preparing strong in-plane spin phase variations is proposed. As a result, periodic patterns of increased motion sensitivity appear, which are interleaved with bands of low phase-to-noise ratio. Spatial filters commonly used in MR elastography (MRE) remove these bands and leave wave images equivalent to a uniform phase response in bSSFP-MRE. Since phase preparation gradients locally enhance motion sensitivity, the technique can be employed for selectively increasing the wave signal amplitude in MRE. The method is applied without the need for previous shimming, which reduces the examination time. In vivo phase prepared bSSFP-MRE is demonstrated in human liver and heart.     

Global Theory of Lattice-Finite Noetherian Rings

We introduce and study lattice-finite Noetherian rings and show that they form a onedimensional analogue of representation-finite Artinian rings. We prove that every lattice-finite Noetherian ring R has Krull dimension ≼ 1, and that R modulo its Artinian radical is an order in a semi-simple ring. Our main result states that maximal overorders of R exist and have to be Asano orders, while they need not be fully bounded. This will be achieved by means of an idempotent ideal I(R), an invariant or R which is new even for classical orders R. This ideal satisfies I(R) = R whenever R is maximal. Presented by H. Tachikawa     

Error estimation of floating-point summation and dot product

We improve the well-known Wilkinson-type estimates for the error of standard floating-point recursive summation and dot product by up to a factor 2. The bounds are valid when computed in rounding to nearest, no higher order terms are necessary, and they are best possible. For summation there is no restriction on the number of summands. The proofs are short by using a new tool for the estimation of errors in floating-point computations which cures drawbacks of the “unit in the last place (ulp)”. The presented estimates are nice and simple, and closer to what one may expect.     

Entwicklung eines universellen, preiswerten Interfaces zur Kopplung von Personal Computern mit Analysenger?ten

Summary This paper presents an expansion of the electronic interface I-O-16 described in some former publications. This new system makes it possible to link an experimental set-up for cyclic voltammetry at the interface between two immiscible electrolyte solutions and a personal computer. Thus the data recording is managed as well as the generation of the potential scan by the computer. A following mathematical treatment allows a numeric correction of the ohmic drop when using a special glass cell for the measurements.

---

---

Teil III siehe [4]

---

Herrn Prof. Dr. Rolf Neeb zum 60. Ggeburtstagb gewidmet     

Behaviour of some organic micropollutants in river sediments and groundwater

Summary Organic micropollutants can reach the ground-water zone by various routes including direct contact with the surface water. River sediments play a substantial role, not only as a concentrating medium but also in their elimination of these substances. The behaviour of polycyclic aromatic hydrocarbons and halogenated compounds is investigated in laboratory experiments, filter plants, sediments and in the ground water. For analyses, Chromatographic methods (GC, TLC, HPLC) and mass spectrometry are employed. Statistical techniques such as principal component analysis and time series analysis are employed for data reduction and evaluation. The application of these methods together with empirical sorption and degradation experiments allow the influence of organic micropollutants on the ground water to be estimated.

---

Verhalten einiger organischer Schadstoffe in Flußsedimenten und Grundwasser

Zusammenfassung Organische Schadstoffe können auf vielfache Art in den Grundwasserbereich gelangen, unter anderem durch unmittelbaren Kontakt mit Oberflächengewässern. Flußsedimente spielen in diesem Zusammenhang eine wesentliche Rolle als Medien zur Anreicherung, aber auch zur Eliminierung dieser Substanzen. Es wird berichtet über das Verhalten polycyclischer aromatischer Kohlenwasserstoffe und halogenhaltiger Schadstoffe in Laborversuchen, Filtereinrichtungen, Sedimenten und im Grundwasserbereich. Als Analysenverfahren werden chromatographische Methoden (GC, TLC, HPLC) sowie die Massenspektrometrie verwendet. Zur Datenauswertung werden statistische Verfahren wie die Hauptkomponentenanalyse und die Zeitreihenanalyse herangezogen. Diese Methoden ermöglichen es, gemeinsam mit empirischen Versuchen zum Sorptions- und Abbauverhalten, die Beeinflussung des Grundwassers mit organischen Schadstoffen abzuschätzen.

     

Expansion and Estimation of the Range of Nonlinear Functions

Many verification algorithms use an expansion , for , where the set of matrices is usually computed as a gradient or by means of slopes. In the following, an expansion scheme is described which frequently yields sharper inclusions for . This allows also to compute sharper inclusions for the range of over a domain. Roughly speaking, has to be given by means of a computer program. The process of expanding can then be fully automatized. The function need not be differentiable. For locally convex or concave functions special improvements are described. Moreover, in contrast to other methods, may be empty without implying large overestimations for . This may be advantageous in practical applications.

     

Cyclotriveratrylene (CTV) as a new chiral triacid scaffold capable of inducing triple helix formation of collagen peptides containing either a native sequence or Pro-Hyp-Gly repeats

A new triacid scaffold is described based on the cone-shaped cyclotriveratrylene (CTV) molecule that facilitates the triple helical folding of peptides containing either a unique blood platelet binding collagen sequence or collagen peptides composed of Pro-Hyp-Gly repeats. The latter were synthesized by segment condensation using Fmoc-Pro-Hyp-Gly-OH. Peptides were coupled to this CTV scaffold and also coupled to the Kemp's triacid (KTA) scaffold. After assembly of peptide H-Gly-[Pro-Hyp-Gly]2-Phe-Hyp-Gly-Glu(OAll)-Arg-Gly-Val-Glu (OAll)-Gly-[Pro-Hyp-Gly]2-NH2 (13) by an orthogonal synthesis strategy to both triacid scaffolds, followed by deprotection of the allyl groups, the molecular constructs spontaneously folded into a triple helical structure. In contrast, the non-assembled peptides did not. The melting temperature (Tm) of (+/-) CTV[CH2C(O)N(H)Gly-[Pro-Hyp-Gly]2-Phe-Hyp-Gly-Glu-Arg-Gly-Val-Glu-Gly- [Pro-Hyp-Gly]2-NH2]3 (14) is 19 degrees C, whereas KTA[Gly-Gly-[Pro-Hyp-Gly]2-Phe-Hyp-Gly-Glu-Arg-Gly-Val-Glu-Gly- [Pro-Hyp-Gly]2-NH2]3 (15) has a Tm of 20 degrees C. Thus, it was shown for the first time that scaffolds were also effective in stabilizing the triple helix of native collagen sequences. The different stabilizing properties of the two CTV enantiomers could be measured after coupling of racemic CTV triacid to the collagen peptide, and subsequent chromatographic separation of the diastereomers. After assembly of the two chiral CTV scaffolds to the model peptide H-Gly-Gly-(Pro-Hyp-Gly)5-NH2 (24), the (+)-enantiomer of CTV 28b was found to serve as a better triple helix-inducing scaffold than the (-)-enantiomer 28a. In addition to an effect of the chirality of the CTV scaffold, a certain degree of flexibility between the CTV cone and the folded peptide was also shown to be of importance. Restricting the flexibility from two to one glycine residues resulted in a significant difference between the two collagen mimics 20a and 20b, whereas the difference was only slight when two glycine residues were present between the CTV scaffold and the peptide sequence in collagen mimics 30a and 30b.