scholarly journals The Role of Proteins in Biosilicification

Scientifica ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
Daniel Otzen
Keyword(s):  
Self Assembly ◽  
Organic Matrix ◽  
Specific Protein ◽  
Colloidal Systems ◽  
Protein Properties ◽  
Modified Peptides ◽  
Fundamental Biology ◽  
Living Organisms ◽  
Insight Into

Although the use of silicon dioxide (silica) as a constituent of living organisms is mainly restricted to diatoms and sponges, the ways in which this process is controlled by nature continue to inspire and fascinate. Both diatoms and sponges carry out biosilificiation using an organic matrix but they adopt very different strategies. Diatoms use small and heavily modified peptides called silaffins, where the most characteristic feature is a modulation of charge by attaching long chain polyamines (LCPAs) to lysine groups. Free LCPAs can also cooperate with silaffins. Sponges use the enzyme silicatein which is homologous to the cysteine protease cathepsin. Both classes of proteins form higher-order structures which act both as structural templates and mechanistic catalysts for the polycondensation reaction. In both cases, additional proteins are continuously being discovered which modulate the process further. This paper concentrates on the role of these proteins in the biosilification process as well as in various applications, highlighting areas where focus on specific protein properties may provide further insight. The field of biosilification is a crossroads of different disciplines, where insight into the energetics and mechanisms of molecular self-assembly combine with fundamental biology, complex multicomponent colloidal systems, and an impressive array of potential technological applications.

From Fundamental Properties to Applications of Surface Activity Investigations: The Kinetic and Thermodynamic Aspects

2020 ◽  
Vol 10 (1) ◽  
pp. 3-9
Author(s):  
Hary Razafindralambo
Keyword(s):  
Chemical Structure ◽  
Fundamental Property ◽  
Fluid Interfaces ◽  
Colloidal Systems ◽  
Fundamental Properties ◽  
Amphiphilic Molecules ◽  
Boundary Limits ◽  
Mixed Systems ◽  
Insight Into

Interfaces, or surfaces in particular (fluid-solid interfaces), are the boundary limits of two immiscible phases characterized by the surface free energy. Getting insight into their fundamental property is of great importance for both scientific and industrial activities. Such an approach enables us to control the formation and stabilization of colloidal systems, which consist of producing homogenous dispersions from at least two initially immiscible phases. In this mini-review, the kinetic and thermodynamic aspects of fluid surfaces are overviewed. Successively, the main phenomena occurring at the interfaces and the appropriate methodology of investigations, the role of amphiphilic molecules in modifying surface properties and generating various functionalities as a function of their chemical structure, size, and shape, and the current approaches for characterizing interactions as well as synergism or antagonism within mixed systems are treated. Relevant relationships of dynamic fundamental properties to macroscopic consequences at the solid and fluid interfaces of single and mixed amphiphile systems are illustrated.

scholarly journals Proteins of Excitable Membranes

1969 ◽  
Vol 54 (1) ◽  
pp. 187-224 ◽  
Author(s):  
David Nachmansohn
Keyword(s):  
Electrical Activity ◽  
Essential Role ◽  
Enzyme Inhibitors ◽  
Specific Protein ◽  
Receptor Protein ◽  
Excitable Membranes ◽  
Protein Properties ◽  
Ion Movements ◽  
Hydrolysis Of

Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment.

An insight into the role of riboflavin ligand in the self-assembly of poly(lactic-co-glycolic acid)-based nanoparticles – a molecular simulation and experimental approach

Soft Matter ◽  
2020 ◽  
Vol 16 (22) ◽  
pp. 5250-5260 ◽  
Author(s):  
Sima Rezvantalab ◽  
Mostafa Keshavarz Moraveji ◽  
Mohammad Khedri ◽  
Reza Maleki
Keyword(s):  
Molecular Simulation ◽  
Self Assembly ◽  
Targeted Delivery ◽  
Glycolic Acid ◽  
Experimental Approach ◽  
The Self ◽  
Insight Into

Nanoparticles (NPs) used for targeted delivery purposes are rapidly gaining importance in diagnostic and therapeutic fields.

Insight into the Role of Hydrogen Bonding in the Molecular Self-Assembly Process of Sulfamethazine Solvates

2017 ◽  
Vol 17 (12) ◽  
pp. 6151-6157 ◽  
Author(s):  
Xia Zhang ◽  
Ling Zhou ◽  
Chang Wang ◽  
Yang Li ◽  
Yanan Wu ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Assembly Process ◽  
Insight Into

Hydrogen bonded supramolecular structures: a further insight into the diamine-diol recognition and self-assembly

2000 ◽  
Vol 78 (6) ◽  
pp. 723-731 ◽  
Author(s):  
Stefano Roelens ◽  
Paolo Dapporto ◽  
Paola Paoli
Keyword(s):  
Molecular Recognition ◽  
Gas Phase ◽  
Self Assembly ◽  
Supramolecular Assembly ◽  
Supramolecular Structures ◽  
Unique Role ◽  
X Ray ◽  
Molecular Code ◽  
Insight Into

A new H-bonded supramolecular assembly of the diamine-diol family has been obtained from (1R,2R)-1,2-diaminocyclohexane (DAC) and (S)-1-phenyl-1,2-ethanediol (PED). The structure was characterized by single-crystal X-ray analysis and showed the typical architecture of DAC based assemblies, consisting of a three-stranded helicate coiling around a H-bonded core, with a predictable helicity sense determined by the configuration of DAC. The new assembly, while reconfirming the unique role of DAC as a powerful assembler of supramolecular structures, demonstrated that the C2 symmetry of diol partners employed so far is not essential for assembling helicates, although chirality is. In the case of the adduct between (1R,2R)-1,2-diaminocyclohexane and (2R,3R)-2,3-butanediol, molecular recognition and self-assembly have been shown to take place even in the absence of solvent, in the gas phase, where long crystals were formed by spontaneous organized aggregation of diamine-diol units. A thorough analysis of the results from the present and previous investigations has lead to a deeper understanding of the key features of the diamine-diol molecular code and of the requirements for recognition and assembly.Key words: supramolecular, hydrogen bonding, molecular recognition, self-assembly, diamines, diols.

scholarly journals Effect of Surface Roughness on Aggregation of Polypeptide Chains: A Monte Carlo Study

Biomolecules ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 596
Author(s):  
Nguyen Truong Co ◽  
Mai Suan Li
Keyword(s):  
Surface Roughness ◽  
Self Assembly ◽  
Molecular Mechanisms ◽  
Monte Carlo Study ◽  
The Self ◽  
Living Organisms ◽  
Polypeptide Chains ◽  
The Impact ◽  
Kinetics Of

The self-assembly of amyloidogenic peptides and proteins into fibrillar structures has been intensively studied for several decades, because it seems to be associated with a number of neurodegenerative diseases, such as Alzheimer’s and Parkinson’s disease. Therefore, understanding the molecular mechanisms of this phenomenon is important for identifying an effective therapy for the corresponding diseases. Protein aggregation in living organisms very often takes place on surfaces like membranes and the impact of a surface on this process depends not only on the surface chemistry but also on its topology. Our goal was to develop a simple lattice model for studying the role of surface roughness in the aggregation kinetics of polypeptide chains and the morphology of aggregates. We showed that, consistent with the experiment, an increase in roughness slows down the fibril formation, and this process becomes inhibited at a very highly level of roughness. We predicted a subtle catalytic effect that a slightly rough surface promotes the self-assembly of polypeptide chains but does not delay it. This effect occurs when the interaction between the surface and polypeptide chains is moderate and can be explained by taking into account the competition between energy and entropy factors.

scholarly journals Recruitment of Class I Hydrophobins to the Air:Water Interface Initiates a Multi-step Process of Functional Amyloid Formation

2011 ◽  
Vol 286 (18) ◽  
pp. 15955-15963 ◽  
Author(s):  
Vanessa K. Morris ◽  
Qin Ren ◽  
Ingrid Macindoe ◽  
Ann H. Kwan ◽  
Nolene Byrne ◽  
...  
Keyword(s):  
Self Assembly ◽  
Structural Rearrangement ◽  
Class I ◽  
Amyloid Formation ◽  
Interface Properties ◽  
Functional Amyloid ◽  
Remarkable Case ◽  
Macromolecular Assembly ◽  
Insight Into

Class I fungal hydrophobins form amphipathic monolayers composed of amyloid rodlets. This is a remarkable case of functional amyloid formation in that a hydrophobic:hydrophilic interface is required to trigger the self-assembly of the proteins. The mechanism of rodlet formation and the role of the interface in this process have not been well understood. Here, we have studied the effect of a range of additives, including ionic liquids, alcohols, and detergents, on rodlet formation by two class I hydrophobins, EAS and DewA. Although the conformation of the hydrophobins in these different solutions is not altered, we observe that the rate of rodlet formation is slowed as the surface tension of the solution is decreased, regardless of the nature of the additive. These results suggest that interface properties are of critical importance for the recruitment, alignment, and structural rearrangement of the amphipathic hydrophobin monomers. This work gives insight into the forces that drive macromolecular assembly of this unique family of proteins and allows us to propose a three-stage model for the interface-driven formation of rodlets.

Virulence factors and biofilm production among Escherichia coli strains causing bacteraemia of urinary tract origin

2008 ◽  
Vol 57 (11) ◽  
pp. 1329-1334 ◽  
Author(s):  
Matija Rijavec ◽  
Manca Müller-Premru ◽  
Breda Zakotnik ◽  
Darja Žgur-Bertok
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Specific Protein ◽  
Immunocompromised Patients ◽  
Virulence Determinants ◽  
Biofilm Production ◽  
Patient Status ◽  
Encoding Genes ◽  
Insight Into

The aim of the present study was to gain an insight into the role of virulence determinants and biofilm production in bacteraemia of urinary tract origin. For this purpose 105 Escherichia coli isolates from patients with bacteraemia of urinary tract origin, isolated at the Institute of Microbiology and Immunology, University of Ljubljana, Slovenia, were investigated. A total of 88 strains (84 %) were isolated from immunocompromised patients and 17 (16 %) from non-immunocompromised patients. The prevalence of virulence factor (VF)-encoding genes and associations with phylogenetic background, antibiotic resistance, biofilm production and patient status were analysed by PCR and bioassay. Biofilm was produced by 55 (53 %) of the strains. No combination of VFs was highly associated with biofilm production. Of the tested VF-encoding genes, usp, papC and the adhesin-encoding sfa/foc were significantly more prevalent among strains from non-immunocompromised patients. Our results indicate that the uropathogenic specific protein (USP) may be, as judged by predominance and associations of the usp gene, an important VF contributing significantly to bacteraemia of urinary tract origin.

scholarly journals Retention of function without normal disc morphogenesis occurs in cone but not rod photoreceptors

2006 ◽  
Vol 173 (1) ◽  
pp. 59-68 ◽  
Author(s):  
Rafal Farjo ◽  
Jeff S. Skaggs ◽  
Barbara A. Nagel ◽  
Alexander B. Quiambao ◽  
Zack A. Nash ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Outer Segment ◽  
Specific Protein ◽  
Rod Photoreceptors ◽  
Rods And Cones ◽  
Insight Into ◽  
Distinct Role

It is commonly assumed that photoreceptor (PR) outer segment (OS) morphogenesis is reliant upon the presence of peripherin/rds, hereafter termed Rds. In this study, we demonstrate a differential requirement of Rds during rod and cone OS morphogenesis. In the absence of this PR-specific protein, rods do not form OSs and enter apoptosis, whereas cone PRs develop atypical OSs and are viable. Such OSs consist of dysmorphic membranous structures devoid of lamellae. These tubular OSs lack any stacked lamellae and have reduced phototransduction efficiency. The loss of Rds only appears to affect the shape of the OS, as the inner segment and connecting cilium remain intact. Furthermore, these structures fail to associate with the specialized extracellular matrix that surrounds cones, suggesting that Rds itself or normal OS formation is required for this interaction. This study provides novel insight into the distinct role of Rds in the OS development of rods and cones.

scholarly journals Mechanosensitive remodeling of the bacterial flagellar motor is independent of direction of rotation

2021 ◽  
Author(s):  
Navish Wadhwa ◽  
Yuhai Tu ◽  
Howard C. Berg
Keyword(s):  
Self Assembly ◽  
External Load ◽  
Protein Complexes ◽  
General Strategy ◽  
Flagellar Motor ◽  
Functional Regulation ◽  
Bacterial Flagellar Motor ◽  
Living Organisms ◽  
Broad Interest ◽  
Insight Into

Motility is critical for the survival and dispersal of bacteria, and it plays an important role during infection. How bacteria regulate motility is thus a question of broad interest. Regulation of bacterial motility by chemical stimuli is well studied, but recent work has added a new dimension to the problem of motility control. The bidirectional flagellar motor of the bacterium Escherichia coli recruits or releases torque-generating units (stator units) in response to changes in load. Here, we show that this mechanosensitive remodeling of the flagellar motor is independent of direction of rotation. Remodeling rate constants in clockwise rotating motors and in counterclockwise rotating motors, measured previously, fall on the same curve if plotted against torque. Increased torque decreases the off rate of stator units from the motor, thereby increasing the number of active stator units at steady state. A simple mathematical model based on observed dynamics provides quantitative insight into the underlying molecular interactions. The torque-dependent remodeling mechanism represents a robust strategy to quickly regulate output (torque) in response to changes in demand (load).SignificanceMacromolecular machines carry out most of the biological functions in living organisms. Despite their significance, we do not yet understand the rules that govern the self-assembly of large multi-protein complexes. The bacterial flagellar motor tunes the assembly of its torque-generating stator complex with changes in external load. Here, we report that clockwise and counterclockwise rotating motors have identical remodeling response to changes in the external load, suggesting a purely mechanical mechanism for this regulation. Autonomous control of self-assembly may be a general strategy for tuning the functional output of protein complexes. The flagellar motor is a prime example of a macromolecular machine in which the functional regulation of assembly can be rigorously studied.

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