Molecular chaperone prefoldin-assisted biosynthesis of gold nanoparticles with improved size distribution and dispersion

Backbone and methyl resonances assignment of the 87 kDa prefoldin from Pyrococcus horikoshii

Prefoldin is a heterohexameric protein assembly which acts as a co-chaperonin for the well conserved Hsp60 chaperonin, present in archaebacteria and the eukaryotic cell cytosol. Prefoldin is a holdase, capturing client proteins and subsequently transferring them to the Hsp60 chamber for refolding. The chaperonin family is implicated in the early stages of protein folding and plays an important role in proteostasis in the cytosol. Here, we report the assignment of ¹H_N, ¹⁵N, ¹³C', ¹³C_α, ¹³C_β, ¹H_methyl, and ¹³C_methyl chemical shifts of the 87 kDa prefoldin from the hyperthermophilic archaeon Pyrococcus horikoshii, consisting of two α and four β subunits. 100% of the [¹³C, ¹H]-resonances of A^β, I^δ1, I^δ2, T^γ2, V^γ2 methyl groups were successfully assigned for both subunits. For the β subunit, showing partial peak doubling, 80% of the backbone resonances were assigned. In the α subunit, large stretches of backbone resonances were not detectable due to slow (μs-ms) time scale dynamics. This conformational exchange limited the backbone sequential assignment of the α subunit to 57% of residues, which corresponds to 84% of visible NMR signals.

Molecular detection using aptamer-modified gold nanoparticles with an immobilized DNA brush for the prevention of non-specific aggregation

Gold nanoparticles (AuNPs) are often used for biosensing. In particular, aptamer-modified AuNPs are often used for colorimetric molecular detection, where target molecule-induced AuNP aggregates can be recognized by a color change from red to blue. However, non-specific aggregation could be induced by various compounds, leading to false-positive results. In this work we employed high-density ssDNA modification on the AuNP surface to prevent non-specific aggregation. The covalently immobilized DNA brush was used as an anchor for an aptamer specific for the target molecule. Herein, as a proof-of-concept study, we demonstrated detection of estradiol (E2), one of the endocrine-disrupting estrogen molecules as a model target, in the presence of antibiotic kanamycin (KN) as a model of co-contaminating compounds that induce non-specific aggregation of AuNPs. We also developed a smartphone dark field microscope (DFM) to visualize AuNP aggregation. Our previous study demonstrated that the observation of light scattering by AuNP aggregates with DFM can be applied for versatile molecular detection. In this work, we could successfully detect E2 with the smartphone DFM, and the results were verified by the results from a conventional benchtop DFM. This study would contribute to the future field applicability of AuNP-based sensors.

We demonstrated molecular detection using aptamer-modified gold nanoparticles with DNA-brush for the prevention of non-specific aggregation and smartphone darkfield microscopy.

Protein-Functionalized Gold Nanoparticles for Antibody Detection Using the Darkfield Microscopic Observation of Nanoparticle Aggregation

Gold nanoparticles (AuNPs) are commonly used in biosensing applications. In this study, AuNPs were synthesized by using reduced bovine serum albumin (rBSA) as the reducing agent. The rBSA conjugated with AuNPs via Au-Sulfur interactions to form rBSA-functionalized AuNPs (rBSA-AuNPs). The interaction of the rBSA moieties on the rBSA-AuNP surface with an anti-BSA antibody (anti-BSA) led to AuNP aggregation, which enabled the successful detection of anti-BSA at a concentration as low as 20 nM through darkfield microscopy (DFM). This study demonstrates the potential applications of protein-functionalized AuNPs in the bioanalysis of substances through DFM.

Graphene templated growth of copper sulphide 'flowers' can suppress electromagnetic interference

With increasing usage of electronic gadgets in various fields, the problem of electromagnetic interference (EMI) has become eminent. To suppress this interference, lightweight materials that are non-corrosive in nature and easy to fabricate, design, integrate and process are in great demand. In the present study, we have grown copper sulphide 'flowers' on graphene oxide by a facile one pot hydrothermal technique. The growth time of the "flower-like" structure was optimised based on structural (XRD) and morphological analysis (SEM). Then, the as-prepared structures were dispersed in a PVDF matrix using melt blending. The bulk AC electrical conductivity and EMI shielding ability of the prepared composite were assessed, and it was observed that the nanocomposites exhibited an EMI shielding effectiveness up to -25 dB manifesting in 86% absorption of the incoming EM waves at a thickness of only 1 mm. Moreover, it was also observed that addition of hybrid nanoparticles has a better effect on the electromagnetic (EM) shielding performance compared to when the nanoparticles are added separately in terms of both total shielding effectiveness as well as absorption performance. A minimum skin depth of 0.38 mm was observed in the case of the hybrid nanostructure.

The functions and mechanisms of prefoldin complex and prefoldin-subunits

The correct folding is a key process for a protein to acquire its functional structure and conformation. Prefoldin is a well-known chaperone protein that regulates the correct folding of proteins. Prefoldin plays a crucial role in the pathogenesis of common neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, and Huntington's disease). The important role of prefoldin in emerging fields (such as nanoparticles, biomaterials) and tumors has attracted widespread attention. Also, each of the prefoldin subunits has different and independent functions from the prefoldin complex. It has abnormal expression in different tumors and plays an important role in tumorigenesis and development, especially c-Myc binding protein MM-1. MM-1 can inhibit the activity of c-Myc through various mechanisms to regulate tumor growth. Therefore, an in-depth analysis of the complex functions of prefoldin and their subunits is helpful to understand the mechanisms of protein misfolding and the pathogenesis of diseases caused by misfolded aggregation.