185,463 research outputs found
RECONSTITUTION OF ALLOPHYCOCYANIN FROM Mastigocladus laminosus WITH ISOLATED LINKER POLYPEPTIDE
No full textThe core linker polypeptide Lc 8.9 was isolated from Mastigocladus laminosus and purified on a preparative scale. A method for the reconstitution of allophycocyanin (AP)—linker complexes from isolated polypeptides was developed. The complex (αAP(βAP)3 Lc 8.9 was reconstituted and compared to (αAPβAP) and (αAPβAP)3 by sucrose density gradient ultracentrifugation, absorption, fluorescence emission and circular dichroism spectroscopy. Differences in the spectra of reconstituted and of directly isolated AP complexes are discussed
Fine mapping of posttranslational modifications of the linker histone H1 from Drosophila melanogaster.
No full textThe linker histone H1 binds to the DNA in between adjacent nucleosomes and contributes to chromatin organization and transcriptional control. It is known that H1 carries diverse posttranslational modifications (PTMs), including phosphorylation, lysine methylation and ADP-ribosylation. Their biological functions, however, remain largely unclear. This is in part due to the fact that most of the studies have been performed in organisms that have several H1 variants, which complicates the analyses. We have chosen Drosophila melanogaster, a model organism, which has a single H1 variant, to approach the study of the role of H1 PTMs during embryonic development. Mass spectrometry mapping of the entire sequence of the protein showed phosphorylation only in the ten N-terminal amino acids, mostly at S10. For the first time, changes in the PTMs of a linker H1 during the development of a multicellular organism are reported. The abundance of H1 monophosphorylated at S10 decreases as the embryos age, which suggests that this PTM is related to cell cycle progression and/or cell differentiation. Additionally, we have found a polymorphism in the protein sequence that can be mistaken with lysine methylation if the analysis is not rigorous
Linker-Directed Assembly of Twisted <i>ortho</i>-Phenylene-Based Macrocycles
No full texto-Phenylene tetramers have been coassembled with
linkers into macrocycles through imine condensation. Variation of
linker connectivity and length allows both [1 + 1] and [2 + 2] macrocycles
to be obtained, complementing (previously reported) [3 + 3] macrocycles.
For the [1 + 1] macrocycles, linker length has a clear effect on o-phenylene geometry and macrocycle stability. For the [2
+ 2] macrocycles, both homo- and heterochiral configurations are observed,
suggesting limited communication of helix handedness in these systems
Linker-assisted engineering of chimeric xylanase-phytase for improved thermal tolerance of feed enzymes
No full textBiological enzymes are multifunctional macromolecules that can perform hundreds of reactions simultaneously. An enzyme must possess specific characteristics to meet industrial needs, such as stability over a wide pH and temperature range and high specific activity. A phytase and xylanase mixture is generally added to poultry feed to improve the bird’s health and productivity. Despite this, animal farmers have noticed no difference in productivity, and a leading cause is the high temperature at which feed is pulverized, which inactivates enzymes. A thermo-stable enzyme system can overcome these hitches. Commonly, coatings and immobilization reduce losses caused by physical-chemical factors in feed processing and digestion. To this end, we engineered the multifunctional xylanase-phytase domains on a single polypeptide fused by a helical linker. First, the ideal linker sequence was chosen by computing each selected linker’s root mean square deviation (RMSD). The selected helical linker provides sufficient structural flexibility for substrate binding and product release evaluated by molecular docking and molecular dynamic simulation studies. Furthermore, a domain-domain interaction has stabilized the bridging partners, attaining the thermal optima for xylanase and phytase at 90 °C. Even at the above-optimal temperature (100 °C), the recombinant PLX was relatively stable and retained 64.2% and 59.2% activity for xylanase and phytase, respectively, when surveyed for ten hours. So far, to this date, this is the highest degree of thermostability achieved by any recombinant phytase or xylanase. Communicated by Ramaswamy H. Sarma</p
Linker-free Functionalization of Phosphorene Nanosheets by Sialic Acid Biomolecules
No full textThe importance of sialic acid on cell functions has been
recently
unveiled, and consequently, great attention has been paid to its interaction
with tumor cells. In this line of research, we have realized phosphorene
nanosheets functionalized with sialic acid molecules for biological
applications with no need for another linker molecule. The formation
of phosphorene sheets is feasible by using hydrogen plasma treatment
and conversion of amorphous phosphorus on silicon substrates into
highly crystalline nanosheets. Through immersion of these freshly
prepared nanosheets into an aqueous solution containing sialic acid
molecules, the formation of chemical binding between biomolecules
and P atoms is initiated to form a carpet-like coverage. We have studied
these structures by using Raman spectroscopy, electron microscopy,
FTIR-ATR spectroscopy, and X-ray photoelectron spectroscopy. While
XPS supports the passivation of sialic-activated phosphorene nanosheets
(SAP) against oxidation in air or aqueous solutions, the FTIR analysis
corroborates the evolution of P–O–C and P–C bonds
between such biomolecules and the sheet surface. Moreover, the high-resolution
TEM images demonstrate a considerable reduction in the lattice spacing
from 0.32 nm for pristine phosphorene to 0.30 nm. Similarly, Raman
spectroscopy depicts a shift in A2g in-plane vibrations, owing to the evolution
of stress in the passivated sheets. To investigate their biocompatibility,
we examined the toxicity of these bioactivated structures and observed
no or little sign of toxicity. For the latter evaluation, we exploited
MTT, flow cytometry, and animal models for in vivo investigations
Degradable and Thermosensitive Microgels with Tannic Acid as the Sole Cross-Linker
No full textPoly(N-isopropylacrylamide) (PNIPAM)–tannic
acid (TA) microgels were successfully prepared via surfactant-free
emulsion polymerization (SFEP) at 70 °C in aqueous solution using N-isopropylacrylamide (NIPAM) as the monomer and a natural
polyphenol macromolecule, TA, as the sole cross-linker. The cross-linking
network of the PNIPAM–TA microgels was confirmed to contain
both physical cross-linking structures formed via hydrogen-bonding
interactions between TA and PNIPAM chains and chemical cross-linking
structures formed via capturing the radicals of propagating polymer
chains by catechol and pyrogallol groups of TA. Furthermore, TA was
applied to modify the surface of hydrophobic Fe3O4 nanoparticles, leading to hydrophilic Fe3O4@TA composite nanoparticles, which were successfully used as the
cross-linker to fabricate PNIPAM–Fe3O4@TA organic–inorganic hybrid microgels. The obtained PNIPAM–TA
and PNIPAM–Fe3O4@TA organic–inorganic
hybrid microgels had a uniform spherical shape with a relatively narrow
size distribution and exhibited thermosensitive behavior and pH-tunable
degradation. The PNIPAM–TA microgels were stable in the pH
range of 1.3–11.1 but underwent complete degradation with pH
above 11.4. The PNIPAM–Fe3O4@TA hybrid
microgels were partially degraded at pH values of 1.3 and 2.1, stable
in the pH range of 3.1–11.1, and underwent complete degradation
at pH above 11.4. The partial degradation of PNIPAM–Fe3O4@TA organic–inorganic hybrid microgels
under strong acidic conditions was attributed to the disintegration
of Fe3O4 nanoparticles. The complete degradation
of both microgels at pH above 11.4 was attributed to the hydrolysis
of ester groups of TA under strong alkali conditions
ATP-dependent chromatosome remodeling
No full textChromatin serves to package, protect and organize the complex eukaryotic genomes to assure their stable inheritance over many cell generations. At the same time, chromatin must be dynamic to allow continued use of DNA during a cell's lifetime. One important principle that endows chromatin with flexibility involves ATP-dependent `remodeling' factors, which alter DNA-histone interactions to form, disrupt or move nucleosomes. Remodeling is well documented at the nucleosomal level, but little is known about the action of remodeling factors in a more physiological chromatin environment. Recent findings suggest that some remodeling machines can reorganize even folded chromatin fibers containing the linker histone H1, extending the potential scope of remodeling reactions to the bulk of euchromatin
Structural analysis of the PRD-B-C linker region.
No full text<p>(A) Crystal structure of the periplakin linker domain (PDB ID 4Q28). One protomer out of four molecules in the asymmetric unit is shown. (B) Structural alignment of the N-terminal part of periplakin linker domain with PR2 of PRD-A. (C) Structural alignment of the C-terminal part of periplakin linker domain with the N-terminal PR like motif of PRD-A.</p
Nature-Inspired Dual Purpose Strategy toward Cell-Adhesive PCL Networks: C(-linker-)RGD Incorporation via Thiol-ene Crosslinking
No full textIn
an attempt to mimic nature’s ability to adhere
cells,
PCL is often coated with nature-derived polymers or its surface is
functionalized with a cell-binding motif. However, said surface modifications
are limited to the material’s surface, include multiple steps,
and are mediated by harsh conditions. Here, we introduce a single-step
strategy toward cell-adhesive polymer networks where thiol-ene chemistry
serves a dual purpose. First, alkene-functionalized PCL is crosslinked
by means of a multifunctional thiol. Second, by means of a cysteine
coupling site, the cell-binding motif C(-linker-)RGD is covalently
bound throughout the PCL networks during crosslinking. Moreover, the
influence of various linkers (type and length), between the cysteine
coupling site and the cell-binding motif RGD, is investigated and
the functionalization is assessed by means of static contact angle
measurements and X-ray photoelectron spectroscopy. Finally, successful
introduction of cell adhesiveness is illustrated for the networks
by seeding fibroblasts onto the functionalized PCL networks
C-linker region of T7 RNAP.
No full text<p>(A) The C-linker region (residues 251 to 296 in cartoon format) adopts different conformations in the initiation state (yellow, 1QLN, IC3), the elongation state (Pink, 1MSW, EC), and with 7 nt transcript bound (blue, 3E2E, IC7). The P266 and L266 residue is shown in stick format. The amino acids from 255 to 263 are disordered in the P266L structure (3E2E) and shown as dashed line. The direction of rotation of the linker near the hinge region is marked with arrows. The C-terminal domains (residues 300–883) of the three structures were aligned using Pymol (Molecular graphics systems). (B) Conservation of proline residue in the linker region between N-terminal domain and C-terminal domain at positions 266 and 270 in single-subunit RNAPs of phage, bacterium, and eukaryotic mitochondria. The N-terminal 1–300 amino acid sequence of T7 RNAP was used as a query in a BLAST amino acid search of the NCBI database for sequence alignment.</p
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