Degree Of Structural Organization Research Articles

FTIR INVESTIGATION ON CRYSTALLINITY OF HYDROXYPROPYL METHYL CELLULOSE-BASED POLYMERIC BLENDS

Two series of polymeric blends have been prepared based on hydroxypropyl methyl cellulose (HPMC)/polyacrylic acid (PAA) (1:1, 1:2, 1:3, 1:4) and HPMC/sodium alginate (SA) (1:30, 2:30, 3:30, 4:40) and investigated by Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR-FTIR). IR analysis confirmed the interaction between the polymeric components in the blend and the degree of structural organization. Crystallinity changes in the blends were observed as a function of a number of experimental parameters, such as temperature, composition and HPMC concentration, by determining the quantitative crystallinity indexes: Total Crystallinity Index (TCI), Lateral Order Index (LOI) and Hydrogen Bond Index (HBI).

HYDROHYPROPYL CELLULOSE/POLYURETHANE BLENDS. THE BEHAVIOR AFTER ACCELERATED AGEING. A FTIR STUDY

A series of hydroxypropyl cellulose/polyurethane blends (PU_HPC 20/80, PU_HPC 50/50 and PU_HPC 80/20) were investigated by FT-IR spectroscopy after exposure to simulated ageing conditions (UV irradiation, 40 °C and 60% humidity) for 600 h. The degree of structural organization was analyzed through quantitative determination of the crystallinity indexes: total crystallinity index (TCI), lateral order index (LOI) and the hydrogen bond intensity (HBI), as well as by the evolution of the “ordered”, “disordered” and “free” areas in the carbonyl (1600-1800 cm-1) spectral region. The accelerated weathering conditions determined structural modification in the PU_HPC blends in correlation with their composition and the exposure time, both polymeric components being affected by the hydrolysis and oxidation processes.

Structural Polymorphs Suggest Competing Pathways for the Formation of Amyloid Fibrils That Diverge from a Common Intermediate Species.

It is now recognized that many amyloid-forming proteins can associate into multiple fibril structures. Here, we use two-dimensional infrared spectroscopy to study two fibril polymorphs formed by human islet amyloid polypeptide (hIAPP or amylin), which is associated with type 2 diabetes. The polymorphs exhibit different degrees of structural organization near the loop region of hIAPP fibrils. The relative populations of these polymorphs are systematically altered by the presence of macrocyclic peptides which template β-sheet formation at specific sections of the hIAPP sequence. These experiments are consistent with polymorphs that result from competing pathways for fibril formation and that the macrocycles bias hIAPP aggregation toward one pathway or the other. Another macrocyclic peptide that matches the loop region but extends the lag time leaves the relative populations of the polymorphs unaltered, suggesting that the branching point for structural divergence occurs after the lag phase, when the oligomers convert into seeds that template fibril formation. Thus, we conclude that the structures of the polymorphs stem from restricting oligomers along diverging folding pathways, which has implications for drug inhibition, cytotoxicity, and the free energy landscape of hIAPP aggregation.

Age-Related Dynamics of Structural Organization of the Metacognitive Processes and Traits of Personality

Introduction. The paper: (a) considers theoretical and empirical studies on the age-related dynamics of structural organization of the metacognitive processes and traits of personality; (b) focuses on quantitative indices of structural organization of the metacognitive processes and traits of personality for various age groups; and (c) describes general ontogenetic dynamics of metacognitive and meta-regulative processes and traits.
 Methods. An empirical study was carried out at two levels that mutually reinforced each other. Specific patterns of the dynamics of certain parameters of metacognitive processes and traits of personality were identified and interpreted at the analytical level. The structural level of the study included two large methodological modules—namely, the diagnostic and statistical module, and the structural and psychological one.
 Results. The study revealed specific characteristics and patterns underlying the genetic and ontogenetic dynamics of metacognitive and meta-regulative personality traits and processes. The indices of structural organization of parameters of the metacognitive processes and traits of personality changed depending on age. Research findings are presented in tables, structuregrams, and graphs.
 Discussion. The results of the empirical study were considered in the context of the main approaches to studying the metacognitive processes and traits of personality, including the author’s approach. The parameters of the main metacognitive and meta-regulative processes do not change significantly between the age of 20 and 62. However, there is a significant age-related increase in the degree of structural organization of the main parameters of the metacognitive traits and processes of personality. With the increase in participants’ age the general dynamics of the index of coherence of the parameters structure of the metacognitive processes and traits is most pronounced. Besides, the dynamics of the divergence index is significantly less pronounced in all the age groups. It is established that the index of overall organization, which is based on the interaction and mutual co-organization of meta-regulative and metacognitive processes, has the most prominent dynamics.
 Highlights
 
 Given the lack of critical attention to the relationships among basic provisions of metacognitivism, developmental, and genetic psychology, studying the patterns of age-related dynamics of the metacognitive processes and traits of personality is an imperative.
 The individual measures of the extent of manifestation of main metacognitive and meta-regulatory processes do not change substantially in ontogenetic development.
 The general increase in the degree of the structural organization of metacognitive and meta-regulative processes and traits of personality underlies their genetic dynamics, which essentially enables the implementation of two main cognitive functions—the compensatory and the resource supplying.
 All the discovered structural changes in the metacognitive processes and traits of personality during ontogenetic development represent a specific variation of a systemic genetic development, as the general increase in the degree of its structural organization serves the purpose of its systemic manifestation, which is basic for the psyche as a whole.

The small world of osteocytes: connectomics of the lacuno-canalicular network in bone

Osteocytes and their cell processes reside in a large, interconnected network of voids pervading the mineralized bone matrix of most vertebrates. This osteocyte lacuno-canalicular network (OLCN) is believed to play important roles in mechanosensing, mineral homeostasis, and for the mechanical properties of bone. While the extracellular matrix structure of bone is extensively studied on ultrastructural and macroscopic scales, there is a lack of quantitative knowledge on how the cellular network is organized. Using a recently introduced imaging and quantification approach, we analyze the OLCN in different bone types from mouse and sheep that exhibit different degrees of structural organization not only of the cell network but also of the fibrous matrix deposited by the cells. We define a number of robust, quantitative measures that are derived from the theory of complex networks. These measures enable us to gain insights into how efficient the network is organized with regard to intercellular transport and communication. Our analysis shows that the cell network in regularly organized, slow-growing bone tissue from sheep is less connected, but more efficiently organized compared to irregular and fast-growing bone tissue from mice. On the level of statistical topological properties (edges per node, edge length and degree distribution), both network types are indistinguishable, highlighting that despite pronounced differences at the tissue level, the topological architecture of the osteocyte canalicular network at the subcellular level may be independent of species and bone type. Our results suggest a universal mechanism underlying the self-organization of individual cells into a large, interconnected network during bone formation and mineralization.

Modeling particle scattering structure factor for branched bio-inspired polymers in solution: A small angle X-ray scattering study

We present a study which illustrates the modeling of the Particle Scattering Structure Factor of an hyperbranched biopolymer in water solution using the Small Angle X-ray Scattering (SAXS) data. The studied sample was a sodium carboxilate terminated poly(amidoamine) dendrimer (generation 2.5) dispersed in water medium. The experimental inter-dendrimer structure factor S(q) has been analyzed in the framework of liquid integral equation theory for charged systems in solution. From that, we derive an effective interparticle interaction composed of a screened Coulombic plus hard-sphere repulsion potential, which allows the estimation of the dendrimer effective charge Zeff. The present analysis strongly supports the finding that structures and interaction of dendrimer are strongly influenced by charge effects. As a result, this quantity can be considered as a crucial parameter for the modulation of the degree of structural organization in solution, suitable for a number of potential applications. We conclude our form factor analysis with the investigation of the long-range assembly conditions during the growth of the intermediate nanoaggregates generated by the inclusion of aluminosilicate components of zeolite 13X on the surface of dendrimers.

Nanostructure of polystyrene-b-poly(2-hydroxyethyl methacrylate) and derivatives with phosphonic diacid groups

Surface engineering for precise positioning of biomolecules is of particular interest for controlled fabrication of biochips. In this study, a novel approach for the preparation of nanodomains with phosphonic diacid groups that were previously shown to reversibly bind to a family of proteins (annexins) in a calcium-dependent manner is described. The strategy makes use of polystyrene-b-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) precursors prepared by atom transfer radical polymerization (ATRP) to obtain hexagonally packed PS cylinders (fPS = 0.25-0.27) in a PHEMA matrix. The pendant hydroxyl groups of PHEMA are then partially (ca. 20%) converted into phosphonic diacid groups via sequential reactions involving phosphorylation, silylation and methanolysis. This process produces PS-b-P(HEMA-co-PEMA) derivatives that still retain the hexagonal morphology, but their degree of structural organization is reduced comparatively to the precursors.

A gene expression signature associated with structural differentiation of prostate acini predicts postoperative recurrence of prostate cancer

Abstract Glandular malignancies such as prostate carcinoma display a considerable heterogeneity in the degree of structural organization while the prognostic role of the associated molecular changes awaits further exploration. Using a three-dimensional (3-D) tissue organization culture model that permits the structural differentiation of prostate glandular epithelium we profiled the transcriptomes of multicellular organoids formed by untransformed prostate epithelial cells (PECs) or prostate carcinoma cells as well as those cultured as cell monolayers. Interrogation into the multiple (n = 6) sets of differentially expressed genes (DEGs) identified that those altered significantly during the structural differentiation process of polarized PEC acini strongly associated with the probability of recurrence in a cohort of 50 prostate cancer patients receiving radical prostatectomy (RP). By contract, the DEGs related to prostate tumor spheroids did not correlate significantly with prognosis. To further explore this association, we prioritized the genes and applied supervised classification algorithms whereby identified a 39-gene structure-associated prognosis signature (SAPS) that shows a remarkable predictivity for the likelihood of post-RP recurrence (overall accuracy 100%, P < 0.001). The SAPS outperformed standard clinicopathological variables, including Gleason scores, as well as existing multigene prognostic predictors of prostate cancer. Our results suggest a distinct contribution by the glandular structural differentiation program to prostate cancer pathology and the usefulness of a robust and biologically relevant genomic predictor of the prognosis of prostate cancer (Supported by NHRI CA-099-PP-19 and Department of Health of Taiwan H99-TD-C-111-004 to KKC).

Fluorescence studies of ascorbate-melittin interaction

Abstract Tryptophanyl fluorescence quenching by ascorbate has been studied in monomeric and tetrameric forms of melittin. The strong efficiency of ascorbate quenching is inconsistent with a collisional type of mechanism. Moreover, from absorption spectra alteration, temperature dependence of the quenching, lack of diffusion control and the unchanged fluorescence lifetime, it is demonstrated that the mechanism of the process is static (formation of a complex) and not dynamic. Thermodynamic parameters suggest that polar interactions mostly contribute to the formation of the complex (negative ΔH value) but that some hydrophobic interactions also occur in the stabilization of the complex. The bell-shaped relationship of the association constants vs. pH indicates that monoprotonated melittin is quenched more easily and that the active species is the reduced ascorbate monoanion. It can be inferred from the pK values (about 6.8 and 8.0) that the involved ionizable residues are probably Lys-21 and Lys-23. Polarization experiments reveal that ascorbate induces a large phosphate-like effect on melittin self-association, increasing the degree of structural organization of the peptide.

Some Degenerative Phenomena in Drosophila Ovaries

ABSTRACT A description is given of degenerative phenomena in the Drosophila ovary. Three types of degeneration are dealt with: (1) degeneration of the follicle cells; (2) degeneration occurring in the unfertilized egg, a major feature of which is the segregation of the different constituents of the egg into comparatively large masses; and (3) degenerative phenomena in the nurse cells and oocytes of abnormal eggs produced in ovaries homozygous for deep-orange. In all these instances it is noteworthy that a considerable degree of structural organization (formation of double membranes, or sets of parallel or concentric membranes, &c.) occurs in cytoplasm which is clearly degenerating. It is suggested that such organization does not always represent the formation of functioning organelles, but may be a mere consequence of the inherent physicochemical properties of the materials involved. In degenerating deep-orange ovaries masses of fragmented porous membranes are found. These seem to be derived from the nuclear membranes of the nurse cells, which appear to persist even when the rest of the cell is rather completely destroyed. Fragments of nuclear envelopes tend to lie close together and parallel to one another, and it is suggested that this indicates that there is some force of attraction between them, which may be comparable to the forces involved in the formation of stacks of annulate lamellae, or of concentric or parallel double-membrane structures in ergastoplasm, and in chromosome pairing in healthy functional cells.

Shell-structure of Thecidean Brachiopods

IN thecidean brachiopods, which range from the Rhaetic to the present day, the shell-structure is less definite, and shows more variation, than in many other brachiopod sub-orders. Investigations I have carried out of this point1, as part of work undertaken for a “Treatise on Invertebrate Paleontology”, resulted in the conclusion that the structure was initially obscurely pseudopunctate, becoming densely punctate when a certain degree of structural organization was attained. This punctation never shows the regular en quinquonce pattern of the terebratuloids: it was attained in different stocks at different dates.