We show that a pair of overlapping Majorana bound states (MBSs) forming a partially-separated Andreev bound state (ps-ABS) represents a generic low-energy feature in spin-orbit coupled semiconductor-superconductor (SM-SC) hybrid nanowire in the presence of a Zeeman field. In a finite nanowire the ps-ABS interpolates continuously between the "garden variety" ABS, which consists of two MBSs sitting on top of each other, and the topologically protected Majorana zero modes (MZMs), which are separated by a distance given by the length of the wire. The really problematic ps-ABSs consist of component MBSs separated by a distance of the order of the characteristic Majorana decay length ξ, and have nearly zero energy in a significant range of control parameters, such as the Zeeman field and chemical potential, within the topologically trivial phase. Despite being topologically trivial, such ps-ABSs can generate signatures identical to MZMs in local charge tunneling experiments. In particular, the height of the zero bias conductance peak (ZBCP) generated by ps-ABSs has the quantized value, 2e 2 /h, and it can remain unchanged in an extended range of experimental parameters, such as Zeeman field and the tunnel barrier height. We illustrate the formation of such low-energy robust ps-ABSs in two experimentally relevant situations: a hybrid SM-SC system consisting of a proximitized nanowire coupled to a quantum dot and the SM-SC system in the presence of a spatially varying inhomogeneous potential. We then show that, unlike local measurements, a two-terminal experiment involving charge tunneling at both ends of the wire is capable of distinguishing between the generic ps-ABSs and the non-Abelian MZMs. While the MZMs localized at the opposite ends of the wire generate correlated differential conduction spectra, including correlations in energy splittings and critical Zeeman fields associated with the emergence of the ZBCPs, such correlations are absent if the ZBCPs are due to ps-ABSs emerging in the topologically trivial phase. Measuring such correlations is the clearest and most straightforward test of topological MZMs in SM-SC heterostructures that can be done in a currently accessible experimental set-up.arXiv:1711.06256v2 [cond-mat.mes-hall]

a b s t r a c tO-glycosylation is a ubiquitous eukaryotic post-translational modification, whereas early reports of S-linked glycopeptides have never been verified. Prokaryotes also glycosylate proteins, but there are no confirmed examples of sidechain glycosylation in ribosomal antimicrobial polypeptides collectively known as bacteriocins. Here we show that glycocin F, a bacteriocin secreted by Lactobacillus plantarum KW30, is modified by an N-acetylglucosamine b-O-linked to Ser18, and an N-acetylhexosamine S-linked to C-terminal Cys43. The O-linked N-acetylglucosamine is essential for bacteriostatic activity, and the C-terminus is required for full potency (IC 50 2 nM). Genomic context analysis identified diverse putative glycopeptide bacteriocins in Firmicutes. One of these, the reputed lantibiotic sublancin, was shown to contain a hexose S-linked to Cys22.

Mycobacterium tuberculosis, the primary agent of tuberculosis, must acquire iron from the host to cause infection. To do so, it releases high-affinity iron-binding siderophores Mycobacterium tuberculosis, the primary causative agent of tuberculosis, infects one-third of humanity and is one of the world's most important infectious agents. M. tuberculosis is a facultative intracellular pathogen. In the host, it multiplies intracellularly in mononuclear phagocytes, and it also appears to multiply extracellularly at least in lung cavities. Its capacity to infect the host is closely linked to its ability to acquire iron. Serum containing poorly saturated transferrin, such as human serum, is tuberculostatic, and its tuberculostatic effect is neutralized by the addition of iron (1, 2).Free iron is very limited in the host, particularly in extracellular sites, owing to the high affinity with which it is held by host iron-binding proteins, chiefly transferrin and lactoferrin. To obtain iron at sites where it is limited, many pathogens have developed high-affinity iron-binding molecules of their own called siderophores, which can remove iron from host ironbinding molecules. Mycobacteria have been shown by Macham, Ratledge, Barclay, and colleagues (3-5) to produce small water-soluble siderophores called exochelins. This group of investigators has proposed that exochelins bind iron in the extracellular aqueous environment and transport the metal to another high-affinity iron-binding molecule located in the cell wall ofM. tuberculosis-mycobactin (3). Mycobactin is a highly lipophilic molecule thought to facilitate the transport of iron across the cell wall to the interior of the bacterium (6).The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Both exochelins and mycobactins are induced by low concentrations of iron in broth medium (4, 7). There are two general types of exochelins, classified according to their extractability in organic solvents (8). The chloroform-insoluble exochelins, produced by saprophytic mycobacteria, are not extractable into any organic solvent. The chloroform-soluble exochelins, produced by slow-growing pathogenic mycobacteria, including M. tuberculosis, are extractable into chloroform (5).Mycobactins have been extensively studied and their structures delineated (7). In contrast, individual exochelins have not been purified previously and neither their structure nor composition has been described. In this paper, we describe the purification of exochelins of M. tuberculosis from both a virulent (Erdman) and an avirulent (H37Ra) strain and their characterization by MS. MATERIALS AND METHODSMedium and Reagents. Modified iron-deficient Sauton's broth medium (9) was prepared with 1-10 ,uM Fe3+ and without Tween. Mycobactin J was purchased from Allied Monitor (Fayette, MO).Bacteria. M. tuberculosis Erdman (ATCC catalog no. 35801) and H37Ra (A...

We show that partially separated Andreev bound states (ps-ABSs), comprised of pairs of overlapping Majorana bound states (MBSs) emerging in quantum dot-semiconductor-superconductor heterostructures, produce robust zero bias conductance plateaus in end-of-wire charge tunneling experiments. These plateaus remain quantized at 2e 2 /h over large ranges of experimental control parameters. In light of recent experiments reporting the observation of robust 2e 2 /h-quantized conductance plateaus in local charge tunneling experiments, we perform extensive numerical calculations to explicitly show that such quantized conductance plateaus, which are obtained by varying control parameters such as the tunnel barrier height, the super gate potential, and the applied magnetic field, can arise as a result of the existence of ps-ABSs. Because ps-ABSs can form rather generically in the topologically trivial regime, even in the absence of disorder, our results suggest that the observation of a robust quantized conductance plateau does not represent sufficient evidence to demonstrate the existence of non-Abelian topologically-protected Majorana zero modes localized at the opposite ends of a wire. arXiv:1804.03164v1 [cond-mat.mes-hall]

Children with autism are known to have difficulties in sharing attention with others. Yet one joint attention behaviour, the ability to follow another person's head turn and gaze direction, may be achieved without necessarily sharing attention. Why, then, should autistic children have difficulties with it? In this study we examined the extent of this difficulty by testing school-aged autistic children across three different contexts; experiment, observation, and parent interview. We also tested whether the ability to orient to another person's head and gaze could be facilitated by increasing children's attention to environmental targets and social cues. Results for experiment and observation demonstrate that a sizeable proportion of children with autism did not have difficulties with following another's head turn. There was a difference between children with high and low verbal mental ages, however. Whereas children with higher mental ages (over 48 months) were able to orient spontaneously to another person's head turn, children with lower mental ages had difficulties with this response. When cues were added (pointing, language) or when feedback from targets was given, however, their performance improved. Parent interview data indicated that children with autism, whatever their mental age, began to follow head turn and gaze direction years later than typically developing children. Developments in attention and language are proposed as possible factors to account for this developmental delay.