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https://www.readbyqxmd.com/read/28107021/synthesis-of-an-uncharged-tetra-cyclopeptide-acting-as-a-transmembrane-carrier-enhanced-cellular-and-nuclear-uptake
#1
Flaviane Francisco Hilário, Mohamed Dit Mady Traoré, Vincent Zwick, Laurence Berry, Claudia A Simões-Pires, Muriel Cuendet, Nicolas Fantozzi, Rossimiriam Pereira de Freitas, Marjorie Maynadier, Sharon Wein, Henri Vial, Yung-Sing Wong
A small uncharged cyclopeptide scaffold inspired by a natural product and designed to undergo postfunctionalizations was used as a new transmembrane vector. A bioactive and fluorescent triazole aminocoumarin was bound to this carrier to facilitate its moving across cell and subcellular membranes, and this led to an increase in its cell toxicity.
January 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28107013/quaternary-n-2-pyridyl-dabco-salts-one-pot-in-situ-formation-from-pyridine-n-oxides-and-reactions-with-nucleophiles-a-mild-and-selective-route-to-substituted-n-2-pyridyl-n-ethylpiperazines
#2
Dmitry I Bugaenko, Marina A Yurovskaya, Alexander V Karchava
The N-(2-pyridyl)-N'-ethylpiperazines are important structural motifs in several medicinally relevant compounds. Known synthetic methods toward these structures are multistep and generally based on the SNAr-chemistry; their applicability is significantly limited to substrates containing electron-withdrawing groups. Here we describe a new methodology for a rapid and modular access to this privileged scaffold. Importantly, the developed protocol proved to be very general and efficient for the substrates containing substituents of different electronic nature...
January 20, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28106994/enzymatic-halogenation-and-dehalogenation-reactions-pervasive-and-mechanistically-diverse
#3
Vinayak Agarwal, Zachary D Miles, Jaclyn M Winter, Alessandra S Eustáquio, Abrahim A El Gamal, Bradley S Moore
Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution...
January 20, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28106855/pharmacomodulation-of-the-antimalarial-plasmodione-synthesis-of-biaryl-and-n-arylalkylamine-analogues-antimalarial-activities-and-physicochemical-properties
#4
Karène Urgin, Mouhamad Jida, Katharina Ehrhardt, Tobias Müller, Michael Lanzer, Louis Maes, Mourad Elhabiri, Elisabeth Davioud-Charvet
With the aim of increasing the structural diversity on the early antimalarial drug plasmodione, an efficient and versatile procedure to prepare a series of biaryl- and N-arylalkylamines as plasmodione analogues is described. Using the naturally occurring and commercially available menadione as starting material, a 2-step sequence using a Kochi-Anderson reaction and subsequent Pd-catalyzed Suzuki-Miyaura coupling was developed to prepare three representative biphenyl derivatives in good yields for antimalarial evaluation...
January 19, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28106210/multi-step-continuous-flow-synthesis
#5
Joshua Britton, Colin L Raston
Organic chemistry is continually evolving to improve the syntheses of value added and bioactive compounds. Through this progression, a concomitant advancement in laboratory technology has occurred. Many researchers now choose to mediate transformations in continuous-flow systems given the many benefits over round bottom flasks. Furthermore, reaction scale up is often less problematic as this is addressed at the inception of the science. Although single-step transformations in continuous-flow systems are common, multi-step transformations are more valuable...
January 20, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28103033/design-synthesis-and-biological-evaluation-of-small-high-affinity-siglec-7-ligands-toward-novel-inhibitors-of-cancer-immune-evasion
#6
Horst Prescher, Martin Frank, Stephan Gütgemann, Elena Kuhfeldt, Astrid Schweizer, Lars Nitschke, Carsten Watzl, Reinhard Brossmer
Natural killer cells are able to directly lyse tumor cells, thereby participating in the immune surveillance against cancer. Unfortunately, many cancer cells use immune evasion strategies to avoid their eradication by the immune system. A prominent escape strategy of malignant cells is to camouflage themselves with Siglec-7 ligands, thereby recruiting the inhibitory receptor Siglec-7 expressed on the NK cell surface which subsequently inhibits NK-cell-mediated lysis. Here we describe the synthesis and evaluation of the first, high-affinity low molecular weight Siglec-7 ligands to interfere with cancer cell immune evasion...
January 19, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28097798/discovery-of-novel-cinchona-alkaloid-inspired-oxazatwistane-autophagy-inhibitors
#7
Luca Laraia, Kosuke Ohsawa, Georgios Konstantinidis, Lucas Robke, Yao-Wen Wu, Kamal Kumar, Herbert Waldmann
The cinchona alkaloids are a privileged class of natural products and are endowed with diverse bioactivities. However, for compounds with the closely-related oxazatricyclo[4.4.0.0]decane ("oxazatwistane") scaffold, which are accessible from cinchonidine and quinidine by means of ring distortion and modification, biological activity has not been identified. We report the synthesis of an oxazatwistane compound collection through employing state-of-the-art C-H functionalization, and metal-catalyzed cross-coupling reactions as key late diversity-generating steps...
January 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28097748/schinortriterpenoids-a-case-study-in-synthetic-design
#8
REVIEW
Xin Li, Paul Ha-Yeon Cheong, Rich G Carter
Since the pioneering days of total synthesis and retrosynthetic analysis, the community has embraced guiding principles for planning synthetic approaches towards complex natural products. These guideposts have enabled the community to synthesize ever more complex compounds by applying prior knowledge gained in new settings. The recently isolated schinortriterpenoid family of natural products has attracted considerable synthetic attention and provided a rich opportunity to evaluate the lessons learned in the construction of complex, polycyclic scaffolds...
January 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28095754/3d-co-culture-of-meniscal-cells-and-mesenchymal-stem-cells-in-collagen-type-i-hydrogel-on-a-small-intestinal-matrix-a-pilot-study-towards-equine-meniscus-tissue-engineering
#9
Antje Kremer, Iris Ribitsch, Jenny Reboredo, Julia Dürr, Monika Egerbacher, Florien Jenner, Heike Walles
Meniscal injuries are the most frequently encountered soft tissue injuries in the equine stifle joint. Due to the inherent limited repair potential of meniscal tissue, meniscal injuries do not only affect the meniscus itself but also lead to impaired joint homeostasis and secondary osteoarthritis. The presented study compares 3D co-culture constructs of primary equine mesenchymal stem cells (MSC) and meniscus cells (MC) seeded on three different scaffolds - a cell-laden collagen type I hydrogel (Col I gel), a tissue-derived small intestinal matrix scaffold (SIS-muc) and a combination thereof - for their qualification to be applied for meniscus tissue engineering...
January 18, 2017: Tissue Engineering. Part A
https://www.readbyqxmd.com/read/28095650/bone-tissue-engineering-in-oral-peri-implant-defects-in-preclinical-in-vivo-research-a-systematic-review-and-meta-analysis
#10
REVIEW
Siddharth Shanbhag, Nikolaos Pandis, Kamal Mustafa, Jens R Nyengaard, Andreas Stavropoulos
Regeneration and establishment of osseointegration within oral peri-implant bone defects remains a clinical challenge. Bone tissue engineering (BTE) is emerging as a promising alternative to autogenous and/or biomaterial-based bone grafting. The objective of this systematic review was to answer the focused question: in animal models, do cell-based BTE strategies enhance bone regeneration and/or implant osseointegration in experimental peri-implant defects, compared to grafting with autogenous bone or only biomaterial scaffolds? Electronic databases were searched for controlled animal studies reporting on peri-implant defects and implantation of mesenchymal stem cells (MSC) or other cells seeded on biomaterial scaffolds, following PRISMA guidelines...
January 17, 2017: Journal of Tissue Engineering and Regenerative Medicine
https://www.readbyqxmd.com/read/28094964/palladium-ii-catalyzed-intramolecular-oxidative-c-h-c-h-cross-coupling-reaction-of-c3-n-linked-biheterocycles-rapid-access-to-polycyclic-nitrogen-heterocycles
#11
Serena Mantenuto, Cecilia Ciccolini, Simone Lucarini, Giovanni Piersanti, Gianfranco Favi, Fabio Mantellini
A Pd(II)-catalyzed intramolecular oxidative C-H/C-H cross-coupling has been developed for the direct construction of valuable polycyclic heteroarene scaffolds. From a retrosynthetic point of view, the strategic formation of a C-C bond via C(sp(2))-H/C(sp(2))-H dehydrogenative coupling across C3,N-linked biheterocyclic precursors may be useful in de novo syntheses of indole-derived natural products and pharmaceuticals. The reaction exhibited good functional group/heterocycle tolerance, and a proposed mechanism involving an azoylpalladium complex is also supported...
January 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/28094241/gelatin-freeze-casting-of-biomimetic-titanium-alloy-with-anisotropic-and-gradient-pore-structure
#12
Lei Zhang, Ronan Le Coz-Botrel, Charlotte Beddoes, Terje Sjöström, Bo Su
Titanium is a material commonly used for dental and orthopaedic implants. However, due to large differences in properties between the titanium metal and the natural bone, stress shielding has been observed in the surrounding area, resulting in bone atrophy, and thus has raised concerns of the use of this material. Ideally implant materials should possess similar properties to the surrounding tissues in order to distribute the load as the joint would naturally, while also possessing a similar porous structure to the bone to enable interaction with the surrounding material...
January 17, 2017: Biomedical Materials
https://www.readbyqxmd.com/read/28093918/a-general-approach-to-the-aza-diketomorpholine-scaffold
#13
Mathéo Berthet, Baptiste Legrand, Jean Martinez, Isabelle Parrot
A stereoconservative three-step synthesis to access to 1,2,4-oxadiazine-3,6-dione is presented. This underexplored platform could be considered as a constrained oxy-azapeptide or an aza-diketomorpholine, the methodology being then successfully applied to produce enantiopure aza-analogs of diketomorpholine natural products. Importantly, the first crystal structures were obtained and compared to diketomorpholine and diketopiperazine structures. Finally, a straightforward procedure concerning the coupling of this heterocyclic scaffold with various amino acids to afford original pseudodipeptide analogs was described...
January 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/28093887/collagen-hydrogel-scaffold-promotes-mesenchymal-stem-cell-and-endothelial-cell-coculture-for-bone-tissue-engineering
#14
Bao-Ngoc B Nguyen, Rebecca A Moriarty, Tim Kamalitdinov, Julie M Etheridge, John P Fisher
The generation of functional, vascularized tissues is a key challenge for the field of tissue engineering. Before clinical implantations of such tissue engineered bone constructs can succeed, tactics to promote neovascularization need to be strengthened. We have previously demonstrated that the tubular perfusion system (TPS) bioreactor is an effective culturing method to augment osteogenic differentiation and maintain viability of human mesenchymal stem cells (hMSC). Here, we devised a strategy to address the need for a functional microvasculature by designing an in vitro coculture system that simultaneously cultures osteogenic differentiating hMSCs with endothelial cells (ECs)...
January 17, 2017: Journal of Biomedical Materials Research. Part A
https://www.readbyqxmd.com/read/28093364/fabrication-of-nanofibrous-electrospun-scaffolds-from-a-heterogeneous-library-of-co-and-self-assembling-peptides
#15
Mahboubeh Maleki, Antonino Natalello, Raffaele Pugliese, Fabrizio Gelain
: Self-assembling (SAPs) and co-assembling peptides (CAPs) are driving increasing enthusiasm as synthetic but biologically inspired biomaterials amenable of easy functionalization for regenerative medicine. On the other hand, electrospinning (ES) is a versatile technique useful for tailoring the nanostructures of various biomaterials into scaffolds resembling the extracellular matrices found in organs and tissues. The synergistic merging of these two approaches is a long-awaited advance in nanomedicine that has not been deeply documented so far...
January 13, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28093363/alignment-of-collagen-fiber-in-knitted-silk-scaffold-for-functional-massive-rotator-cuff-repair
#16
Zefeng Zheng, Jisheng Ran, Weishan Chen, Yejun Hu, Ting Zhu, Xiao Chen, Zi Yin, Boon Chin Heng, Gang Feng, Huihui Le, Chenqi Tang, Jiayun Huang, Yangwu Chen, Yiting Zhou, Pioletti Dominique, Weiliang Shen, Hong-Wei Ouyang
: Rotator cuff tear is one of the most common types of shoulder injuries, often resulting in pain and physical debilitation. Allogeneic tendon-derived decellularized matrices do not have appropriate pore size and porosity to facilitate cell infiltration, while commercially-available synthetic scaffolds are often inadequate at inducing tenogenic differentiation. The aim of this study is to develop an advanced 3D aligned collagen/silk scaffold (ACS) and investigate its efficacy in a rabbit massive rotator cuff tear model...
January 13, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28089930/scaffolds-containing-chitosan-gelatin-and-graphene-oxide-for-bone-tissue-regeneration-in-vitro-and-in-vivo
#17
S Saravanan, Anjali C, M Vairamani, T P Sastry, K S Subramanian, N Selvamurugan
Critical-sized bone defects are augmented with cell free and cell loaded constructs to bridge bone defects. Improving the properties of three-dimensional scaffolds with multiple polymers and others is of growing interest in recent decades. Chitosan (CS), a natural biopolymer has limitations for its use in bone regeneration, and its properties can be enhanced with other materials. In the present study, the composite scaffolds containing CS, gelatin (Gn) and graphene oxide (GO) were fabricated through freeze-drying...
January 12, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28088099/protein-templated-synthesis-of-metal-based-nanomaterials
#18
REVIEW
Arnout Rd Voet, Jeremy Rh Tame
There is currently intense interest in using protein scaffolds to prepare uniform nanometre-sized clusters of metals or other inorganic material for use as sensors, imaging agents, drugs, magnetic materials or catalysts. Non-templated chemical synthesis of such clusters often results in a product of variable size and quality, but protein molecules have proved adept at nucleating and stabilizing precise nanoclusters of various kinds. Although much research has focused on natural proteins, such as the iron-storage protein ferritin, recent developments in protein design have allowed entirely novel, symmetrical proteins to be used as templates for the first time...
January 11, 2017: Current Opinion in Biotechnology
https://www.readbyqxmd.com/read/28087448/fabrication-and-characterization-of-electrospun-cellulose-nano-hydroxyapatite-nanofibers-for-bone-tissue-engineering
#19
Chenghong Ao, Yan Niu, Ximu Zhang, Xu He, Wei Zhang, Canhui Lu
Nanofibrous scaffolds from cotton cellulose and nano-hydroxyapatite (nano-HA) were electrospun for bone tissue engineering. The solution properties of cellulose/nano-HA spinning dopes and their associated electrospinnability were characterized. Morphological, thermal and mechanical properties of the electrospun cellulose/nano-HA nanocomposite nanofibers (ECHNN) were measured and the biocompatibility of ECHNN with human dental follicle cells (HDFCs) was evaluated. Scanning electron microscope (SEM) images indicated that the average diameter of ECHNN increased with a higher nano-HA loading and the fiber diameter distributions were well within the range of natural ECM (extra cellular matrix) fibers (50-500nm)...
January 10, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28079980/induction-of-mesenchymal-stem-cell-differentiation-in-the-absence-of-soluble-inducer-for-cutaneous-wound-regeneration-by-a-chitin-nanofibers-based-hydrogel
#20
Kangquan Shou, Yao Huang, Baiwen Qi, Xiang Hu, Zhanjun Ma, Ang Lu, Chao Jian, Lina Zhang, Aixi Yu
Transplantation of bone marrow mesenchymal stem cells (BMSCs) has been considered as a promising strategy for wound healing. However, poor viability of engrafted BMSCs and limited capabilities of differentiation into the desired cell types in wounds often hinder their application. Few studies report the induction of BMSCs differentiation into the skin regeneration related cell types using natural biopolymer, e.g., chitin and its derivative. Here we utilized a chitin nanofibers(CNFs) hydrogel as a directive cue to induce BMSCs differentiation for enhancing cutaneous wound regeneration in the absence of cell-differentiating factors...
January 12, 2017: Journal of Tissue Engineering and Regenerative Medicine
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