The Human LL-37(17-29) Antimicrobial Peptide Reveals a Functional Supramolecular Nanostructure

Protein fibrils that perform biological activities present attractive biomaterials. Here we demonstrate, by crystal structures, the self-assembly of the antibacterial human LL-37 active core (residues 17-29) into a stable structure of densely packed helices. The surface of the fibril encompasses alternating hydrophobic and positively charged zigzagged belts, which likely underlie interactions with and subsequent disruption of negatively charged lipid bilayers, such as bacterial membranes. LL-3717-29 correspondingly formed wide, ribbon-like, thermostable fibrils in solution, which co-localized with bacterial cells, and structure-guided mutagenesis analyses supported the role of self-assembly in antibacterial activity. LL-3717-29 resembled, in sequence and in the ability to form amphipathic helical fibrils, the bacterial cytotoxic PSMα3 peptide that assembles into cross-α amyloid fibrils. This suggests helical, self-assembling, basic building blocks across kingdoms of life and point to potential structural mimicry mechanisms. The findings offer a scaffold for functional and durable nanostructures for a wide range of medical and technological applications.

Sino-orbital Zygomycosis: an atypical presentation of a rare disease in an immunocompetent child

Zygomycosis is a rare life threatening fungal infection in an immunocompromised child. The clinical manifestations of zygomycosis mainly are rhino cerebral, pulmonary, cutaneous, gastrointestinal, and cardiac disease. The diagnosis of zygomycosis is confirmed by direct examinations of clinical specimens and histopathological examination of tissue. The characteristic feature of Zygomycetes in tissue is, the formation of wide, ribbon-like, hyaline, aseptate or sparsely septated hyphae with wide-angle (approximately 90°) branching. The current report describes a case of sino-orbital zygomycosis in a 16-month-old immunocompetent child with atypical presentation. Histopathological examination (HPE) of the tissue confirmed the diagnosis of Zygomycetes.

Correlation Between the Sites of Onset of Basal Cell Carcinoma and the Embryonic Fusion Planes in the Auricle

Objectives: This study aims at the identification of the distribution of basal cell carcinomas (BCCs) in the auricle in correlation with the currently most credited sites of the embryonic fusion planes of the auricle. Methods: An overall number of 69 patients with 72 BCCs of the auricle were enrolled in the study over a period of 14 years, from June 2003 to October 2017. All the cases underwent medical preoperative digital photography and the specific location of each BCC was coded on an original full-size anatomical diagram of the auricle derived from the reports by Streeter, Wood-Jones, Park, Porter, and Minoux showing the currently most credited sites of the embryonic fusion planes arbitrarily featured as two 5-mm-wide ribbon-like areas: (1) the hyoid-mandibular fusion plane (HM-FP) running from the upper margin of the tragus toward the concha and then deflecting toward the lower margin of the tragus and (2) the free ear fold-hyoid fusion plane (FEFH-FP) running from the cranial-most portion of the helix to the mid-portion of the ascending helix. The latter fusion planes were comprehensively termed embryological fusion planes (EFP) while all of the remaining surface of the auricle was comprehensively termed non-fusion area (NFA). The surfaces of all of the latter areas were calculated using the ImageJ software. Results: According to our data, the greatest number of BCCs was observed within the currently most credited sites of the embryonic fusion planes of the auricle. The latter sites displayed a 12-fold increased tumor incidence in comparison with the remaining surface of the ear. Conclusions: A correspondence between the sites of onset of BCCs and the sites of merging and/or fusion of embryonal processes was demonstrated in the auricle. Therefore, the latter sites might be considered as high-risk areas for the development of a BCC. Such an evidence provides further support to the hypothesis of an embryological pathogenesis of BCC.

The three-dimensional architecture of chromatin in situ: electron tomography reveals fibers composed of a continuously variable zig-zag nucleosomal ribbon.

The three dimensional (3D) structure of chromatin fibers in sections of nuclei has been determined using electron tomography. Low temperature embedding and nucleic acid-specific staining allowed individual nucleosomes to be clearly seen, and the tomographic data collection parameters provided a reconstruction resolution of 2.5 nm. Chromatin fibers have complex 3D trajectories, with smoothly bending regions interspersed with abrupt changes in direction, and U turns. Nucleosomes are located predominantly at the fiber periphery, and linker DNA tends to project toward the fiber interior. Within the fibers, a unifying structural motif is a two nucleosome-wide ribbon that is variably bent and twisted, and in which there is little face-to-face contact between nucleosomes. It is suggested that this asymmetric 3D zig-zag of nucleosomes and linker DNA represents a basic principle of chromatin folding that is determined by the properties of the nucleosome-linker unit. This concept of chromatin fiber architecture is contrasted with helical models in which specific nucleosome-nucleosome contacts play a major role in generating a symmetrical higher order structure. The transcriptional control implications of a more open and irregular chromatin structure are discussed.