Some observations related to intermittency and multifractality in Si and C-nucleus collisions at

An attempt is made to study the existence of dynamical fluctuations of relativistic particles using the methods of modified multifractal moments, G_q, and scaled factorial moments, F_q, in terms of new scaled variable X(η) suggested by Bialas and Gazdzicki. For this purpose analyses of experimental and UrQMD data involving interactions of ²⁸Si and ¹²C nuclei at with nuclear emulsion are used. The variation of lnG_q and lnF_q with lnM in pseudorapidity (η) phase space reveals power law behaviour. The values of slopes, τ_q and _q determined from the analyses of G_q and F_q moments are discussed. The generalized fractal dimensions, D_q, determined from the above methods are found to decrease with the order of the moments, q, indicating multifractality in multiparticle production. It is also observed that the spectral function f(α_q) for heavier projectile is much broader than for lighter beam due to larger number of participating nucleons present in heavier projectile.     

Study of number of black prongs in two generations of nuclear interactions in photoemulsion irradiated by 72 GeV Ne

This work is a study of new aspects in relativistic nucleus–nucleus interactions using the nuclear emulsion technique and it is aimed at development of a method of search of these interactions. Layers of nuclear photographic emulsion type-BR2 with sizes were irradiated with 72 GeV ²²Ne beam parallel to emulsion surface. The scanning length was 110 mm. The new idea is the counting of black prongs in nuclear–nuclear interactions due to primary projectile ²²Ne ions and due to their α- and Z3 projectile fragments, i.e. their (Z2)-secondary fragments. The ratio of their black prong multiplicity distributions is measured. Black prongs are low-energy Z=1 particles in case of protons with energies below 30 MeV emitted from the residual nuclei of these high-energy interactions. Two divisions of events were used. The first one was over more peripheral events, more central and exceedingly central collisions. The second division was over collisions creating fragments Z2 and without their creation. The ratios between numbers of events in such different subsets, as well the ratios between of different mean values of N_b multiplicities averaged inside these subsets were studied. These results are discussed, also in the context of other thick target experiment, studied with radiochemistry or neutron counting techniques. In addition, different versions of the mean free nuclear ranges of Ne-ions and their heavy secondary fragments have been measured and calculated. We have scheduled the further strategy of search of new phenomena in similar multiplicity distributions at greater statistics of future experiments.     

Synthesis of an Octacyclic C60 Fragment

Fragments of buckminsterfullerene (C₆₀) include the monumental three compounds corannulene, sumanene, and truxene. These three have served as leading molecules in ongoing research for curved, fused, and π-extended polyaromatic materials. Achieving more structural variations that join the ranks of these three archetypes remains challenging. Herein we report synthesis of an octacyclic hydrocarbon that is an unexplored C₆₀-fragment, namely, a 4,11-dihydrodiindeno[7,1,2-ghi:7′,1′,2′-pqr]chrysene (C₂₈H₁₆, which we named Metelykene). The key to success was solution-compatible synthesis in which double pentagonal rings flank hexagonal ones. This solution-phase approach, coupled with the resulting non-planar π-conjugation, is so straightforward that it offers an entry to a derivative such as a cardo aromatic monomer.     

CONFIRM: connecting fragments found in receptor molecules

A novel algorithm for the connecting of fragment molecules is presented and validated for a number of test systems. Within the CONFIRM (Connecting Fragments Found in Receptor Molecules) approach a pre-prepared library of bridges is searched to extract those which match a search criterion derived from known experimental or computational binding information about fragment molecules within a target binding site. The resulting bridge 'hits' are then connected, in an automated fashion, to the fragments and docked into the target receptor. Docking poses are assessed in terms of root-mean-squared deviation from the known positions of the fragment molecules, as well as docking score should known inhibitors be available. The creation of the bridge library, the full details and novelty of the CONFIRM algorithm, and the general applicability of this approach within the field of fragment-based de novo drug design are discussed.     

Unprecedented Combination of Polyketide Natural Product Fragments Identifies the New Hedgehog Signaling Pathway Inhibitor Grismonone

Pseudo-natural products (pseudo-NPs) are de novo combinations of natural product (NP) fragments that define novel bioactive chemotypes. For their discovery, new design principles are being sought. Previously, pseudo-NPs were synthesized by the combination of fragments originating from biosynthetically unrelated NPs to guarantee structural novelty and novel bioactivity. We report the combination of fragments from biosynthetically related NPs in novel arrangements to yield a novel chemotype with activity not shared by the guiding fragments. We describe the synthesis of the polyketide pseudo-NP grismonone and identify it as a structurally novel and potent inhibitor of Hedgehog signaling. The insight that the de novo combination of fragments derived from biosynthetically related NPs may also yield new biologically relevant compound classes with unexpected bioactivity may be considered a chemical extension or diversion of existing biosynthetic pathways and greatly expands the opportunities for exploration of biologically relevant chemical space by means of the pseudo-NP principle.     

NMR Investigation of the Influence of Sulfate Groups at C‐2 and C‐4 on the Conformational Behavior of Fucoidan Fragments with Homo‐(1→3)‐Linked Backbone#

The conformational behavior of 2‐O‐ and 4‐O‐sulfated derivatives of linear (1→3)‐linked di‐, tri‐, and tetrafucosides and 2,3‐branched tetrafucoside was studied by means of theoretical molecular modeling and experimental determination of trans‐glycosidic vicinal coupling constants ³J_C,H. It was shown that O‐sulfation of (1→3)‐linked oligofucosides restricts their conformational flexibility and changes the conformational equilibrium if compared with the parent nonsulfated oligosaccharides. In the case of 2‐O‐sulfated oligofucosides, the conformations of O‐glycoside linkages depend on its location within the oligosaccharide chain and the chain length as well as on the presence of a 2,3‐branch, whereas the conformation of the (1→3)‐linkage in the presence of a 4‐O‐sulfate group only depends on the presence of a 2,3‐branch.     

Removable edges in a spanning tree of a k-connected graph

An edge e of a k-connected graph G is said to be a removable edge if G O e is still k-connected, where G O e denotes the graph obtained from G by the following way： deleting e to get G - e, and for any end vertex of e with degree k - 1 in G - e, say x, deleting x, and then adding edges between any pair of non-adjacent vertices in NG-e （x）. The existence of removable edges of k-connected graphs and some properties of k-connected graphs have been investigated. In the present paper, we investigate the distribution of removable edges on a spanning tree of a k-connected graph （k ≥ 4）.     

Neural Network Classification of Mutagens Using Structural Fragment Data

Abstract

A neural network was applied to a large, structurally heterogeneous data set of mutagens and nonmutagens to investigate structure-property relationships. Substructural data comprising a total of 1280 fragments were used as inputs. The training of the back-propagation networks was directed by an algorithm which selected an optimal subset of fragments in order to maximize their discriminating power, and a good predictive network.

The system comprised three programs: the first used a keyfile of 100 fragments to generate training and test files, the second was the network itself and a procedure for ranking the effectiveness of these fragments and the third randomly replaced the lowest fragments. This cycle was then repeated. After running on a 386/33 PC several networks produced approximately 11% failures in the test set and 6% in the training set.

By simplifying the output of the hidden layer it was possible to describe the hidden layer states in terms of clusters of mutagens and non-mutagens. Some of these clusters were structurally homogeneous and contained known mutagenic and non-mutagenic structural classes. This analysis provided a useful means of demonstrating how the network was classifying the data.     

RP–HPLC–ESI–MS characterization of novel peptide fragments related to rat parotid secretory protein in parasympathetic induced saliva

Two peptides (MW 1211.7 and 928.5 Da) were detected by RP–HPLC–ESI–MS analysis of parotid saliva secreted upon continuous parasympathetic stimulation. The peptide with the higher mass (PSPFr‐A) corresponded to the N‐terminal dodecapeptide (Fragment 1–12) of rat parotid secretory protein (PSP), while the peptide with the lower mass (PSPFr‐B) corresponded to the 4–12 fragment of the same protein. During stimulation, the PSPFr‐A secretion increased, while the PSPFr‐B secretion decreased (HPLC–ESI–MS). In the presence of cycloheximide, PSPFr‐A was not demonstrated, while the PSPFr‐B secretion decreased. In the presence of aprotinin, the PSPFr‐B secretion was almost abolished, while the PSPFr‐A secretion increased to higher levels than those observed in the absence of the inhibitor. In vitro perfusion, with artificial solution, of stimulated rat parotid glands excluded that the fragments were derived from the circulation. Neither peptide occurred in enriched granule preparations from unstimulated glands. The results suggest that at least two pathways – granular and vesicular – are responsible for the generation of the two peptides. PSPFr‐A is the first cleavage product in both pathways. PRPFr‐B is probably generated from granular PSPFr‐A only and, at the end of the granule mediated pathway, by the action of an enzyme of the serine protease class.