An intrinsically disordered nascent protein interacts with specific regions of the ribosomal surface near the exit tunnel

The influence of the ribosome on nascent chains is poorly understood, especially in the case of proteins devoid of signal or arrest sequences. Here, we provide explicit evidence for the interaction of specific ribosomal proteins with ribosome-bound nascent chains (RNCs). We target RNCs pertaining to the intrinsically disordered protein PIR and a number of mutants bearing a variable net charge. All the constructs analyzed in this work lack N-terminal signal sequences. By a combination chemical crosslinking and Western-blotting, we find that all RNCs interact with ribosomal protein L23 and that longer nascent chains also weakly interact with L29. The interacting proteins are spatially clustered on a specific region of the large ribosomal subunit, close to the exit tunnel. Based on chain-length-dependence and mutational studies, we find that the interactions with L23 persist despite drastic variations in RNC sequence. Importantly, we also find that the interactions are highly Mg+2-concentration-dependent. This work is significant because it unravels a novel role of the ribosome, which is shown to engage with the nascent protein chain even in the absence of signal or arrest sequences.

Probing neutron-hidden neutron transitions with the MURMUR experiment

MURMUR is a new passing-through-walls neutron experiment designed to constrain neutron-hidden neutron transitions allowed in the context of braneworld scenarios or mirror matter models. A nuclear reactor can act as a source of hidden neutrons, such that neutrons travel through a hidden world or sector. Hidden neutrons can propagate out of the nuclear core and far beyond the biological shielding. However, hidden neutrons can weakly interact with usual matter, making possible for their detection in the context of low-noise measurements. In the present work, the novelty rests on a better background discrimination and the use of a mass of a material – here lead – able to enhance regeneration of hidden neutrons into visible ones to improve detection. The input of this new setup is studied using both modelizations and experiments, thanks to tests currently performed with the experiment at the BR2 research nuclear reactor (SCK$$\cdot $$ · CEN, Mol, Belgium). A new limit on the neutron swapping probability p has been derived thanks to the measurements taken during the BR2 Cycle 02/2019A: $$p<4.0\times 10^{-10} \; \text {at 95}\%\text { CL}$$ p < 4.0 × 10 - 10 at 95 % CL . This constraint is better than the bound from the previous passing-through-wall neutron experiment made at ILL in 2015, despite BR2 is less efficient to generate hidden neutrons by a factor of 7.4, thus raising the interest of such experiment using regenerating materials.

Hyperpolarisation of weakly binding N-heterocycles using signal amplification by reversible exchange

The scope of the hyperpolarisation method Signal Amplification by Reversible Exchange (SABRE) is dramatically expanded through the use of co-ligands to substrates that weakly interact with the active cataylst.

Reduction of Schottky Barrier Height at Graphene/Germanium Interface with Surface Passivation

Fermi level pinning at metal/semiconductor interfaces forbids a total control over the Schottky barrier height. 2D materials may be an interesting route to circumvent this problem. As they weakly interact with their substrate through Van der Waals forces, deposition of 2D materials avoids the formation of the large density of state at the semiconductor interface often responsible for Fermi level pinning. Here, we demonstrate the possibility to alleviate Fermi-level pinning and reduce the Schottky barrier height by the association of surface passivation of germanium with the deposition of 2D graphene.

Adsorption of Formic Acid on Pd(111) Catalyst in the Gas Phase

It is important to understand the nature of formic acid (HCOOH) adsorption on transition metal surfaces so as to elucidate the mechanism of its decomposition in direct HCOOH fuel cells. Despite the overwhelming interest, not much is known about the adsorption behaviour of HCOOH on Pd(111) surfaces. This work presents a theoretical study of monomeric HCOOH adsorption on Pd(111) surfaces in the gas phase. The stable configurations of the adsorbed molecules on the surface are displayed, with some omitted in previous studies. Our calculations show that the most stable configuration is that with the hydroxyl O and H on C in HCOOH binding to the surface. The modes of adsorption of HCOOH dimer are presented on Pd(111) for the first time. It is found that both the monomer and dimer of HCOOH weakly interact with the surface. Our results are intended to provide valuable insights to understand the reactivity of HCOOH on Pd(111).

Amyloid β-peptides interfere with mitochondrial preprotein import competence by a co-aggregation process

Aβ peptides play a central role in the etiology of Alzheimer disease (AD) by exerting cellular toxicity correlated with aggregate formation. Experimental evidences showed an intraneuronal accumulation of Aβ peptides and toxic effects on mitochondrial functions. Nevertheless, the relevance of intracellular Aβ peptides in the pathophysiology of AD remained controversial. Here, we found that the two major species of Aβ peptides, in particular Aβ42, exhibited a strong negative effect on the preprotein import reactions essential for mitochondrial protein biogenesis. However, Aβ peptides only weakly interact with mitochondria and did not affect the inner membrane potential or the structure of the preprotein translocase complexes. Aβ peptides significantly decreased the import competence of mitochondrial precursor proteins through a specific co-aggregation mechanism. Co-aggregation and import inhibition were significantly stronger in case of the longer peptide Aβ42, correlating with its importance in AD pathology. Our results demonstrate that a direct interference of aggregation-prone Aβ peptides with mitochondrial protein biogenesis represents a crucial aspect of the pathobiochemical mechanisms contributing to cellular damage in AD.

Non-interacting, sp2 carbon on a ferroelectric lead zirco-titanate: towards graphene synthesis on ferroelectrics in ultrahigh vacuum

Carbon layers grown on lead zirco-titanate (PZT) weakly interact with the substrate and exhibit nearly two dimensional character, up to a carbon surface density approaching that of graphene.