scholarly journals Remarkable self-sorting selectivity in covalently linked homochiral and heterochiral pairs driven by Pd2L4 helicate formation

2020 ◽  
Vol 56 (61) ◽  
pp. 8679-8682
Author(s):  
Daiji Ogata ◽  
Junpei Yuasa
Keyword(s):  
Statistical Mixture ◽  
Covalently Linked

Remarkable self-sorting selectivity is demonstrated between LRR and LRS through a Pd2L4 assembly. By contrast, mixing of LRR and LSS with Pd2+ produces a near statistical mixture.

Large-cluster and combined fluorescent and gold immunoprobes

1996 ◽  
Vol 54 ◽  
pp. 892-893
Author(s):  
Richard D. Powell ◽  
James F. Hainfeld ◽  
Carol M. R. Halsey ◽  
David L. Spector ◽  
Shelley Kaurin ◽  
...  
Keyword(s):  
Metal Cluster ◽  
Sulfonyl Chloride ◽  
Gel Filtration ◽  
Cross Linking ◽  
Site Specific ◽  
Fab Fragments ◽  
Cluster Label ◽  
Covalently Linked ◽  
Texas Red ◽  
Fold Excess

Two new types of covalently linked, site-specific immunoprobes have been prepared using metal cluster labels, and used to stain components of cells. Combined fluorescein and 1.4 nm “Nanogold” labels were prepared by using the fluorescein-conjugated tris (aryl) phosphine ligand and the amino-substituted ligand in the synthesis of the Nanogold cluster. This cluster label was activated by reaction with a 60-fold excess of (sulfo-Succinimidyl-4-N-maleiniido-cyclohexane-l-carboxylate (sulfo-SMCC) at pH 7.5, separated from excess cross-linking reagent by gel filtration, and mixed in ten-fold excess with Goat Fab’ fragments against mouse IgG (obtained by reduction of F(ab’)2 fragments with 50 mM mercaptoethylamine hydrochloride). Labeled Fab’ fragments were isolated by gel filtration HPLC (Superose-12, Pharmacia). A combined Nanogold and Texas Red label was also prepared, using a Nanogold cluster derivatized with both and its protected analog: the cluster was reacted with an eight-fold excess of Texas Red sulfonyl chloride at pH 9.0, separated from excess Texas Red by gel filtration, then deprotected with HC1 in methanol to yield the amino-substituted label.

In vitro assembly of 2-D crystals from partially purified EA1 protein secreted by Bacillus anthracis strain Delta Sterne-1

1994 ◽  
Vol 52 ◽  
pp. 276-277
Author(s):  
Mary Beth Downs ◽  
Wilson Ribot ◽  
Joseph W. Farchaus
Keyword(s):  
Cell Wall ◽  
Molecular Sieves ◽  
Cell Envelope ◽  
Single Species ◽  
Supporting Cell ◽  
Surface Layers ◽  
Rabbit Igg ◽  
In Vitro Assembly ◽  
Covalently Linked

Many bacteria possess surface layers (S-layers) that consist of a two-dimensional protein lattice external to the cell envelope. These S-layer arrays are usually composed of a single species of protein or glycoprotein and are not covalently linked to the underlying cell wall. When removed from the cell, S-layer proteins often reassemble into a lattice identical to that found on the cell, even without supporting cell wall fragments. S-layers exist at the interface between the cell and its environment and probably serve as molecular sieves that exclude destructive macromolecules while allowing passage of small nutrients and secreted proteins. Some S-layers are refractory to ingestion by macrophages and, generally, bacteria are more virulent when S-layers are present.When grown in rich medium under aerobic conditions, B. anthracis strain Delta Sterne-1 secretes large amounts of a proteinaceous extractable antigen 1 (EA1) into the growth medium. Immunocytochemistry with rabbit polyclonal anti-EAl antibody made against the secreted protein and gold-conjugated goat anti-rabbit IgG showed that EAI was localized at the cell surface (fig 1), which suggests its role as an S-layer protein.

Structure of rattlesnake venom lectin determined by single particle high-resolution electron microscopy

1996 ◽  
Vol 54 ◽  
pp. 62-63
Author(s):  
Peter D. Moisiuk ◽  
Daniel R. Beniac ◽  
Ross A. Ridsdale ◽  
Martin Young ◽  
Bhushan Nagar ◽  
...  
Keyword(s):  
High Resolution Electron Microscopy ◽  
Lipid Monolayer ◽  
Outer Diameter ◽  
X Ray Diffraction ◽  
Single Particles ◽  
Crotalus Atrox ◽  
3D Reconstructions ◽  
X Ray ◽  
Rattlesnake Venom ◽  
Covalently Linked

Venom from the rattlesnake Crotalus atrox contains a mixture of enzymes that induce a localized effect leading to hemorrhaging, necrosis and edema. As a member of the crotalid family of snake venoms, Crotalus atrox venom contains a C-type lectin that will agglutinate blood cells in a Ca2+-dependent fashion. The lectin is a hydrophilic protein, consisting of two covalently linked, 135 amino acid residues, identical subunits that are rich in aspartic acid, glutamic acid and lysine. Sequence homology with known carbohydrate recognition domains (CRDs) indicates that rattlesnake venom lectin (RSLV) contains a CRD motif that is not linked to accessory domains. Preliminary X-ray diffraction and sedimentation analysis has indicated that lectin from Crotalus atrox forms decamers composed of two five-fold symmetric pentamers. Single particles of RSVL imaged at – 171°C displayed two distinct orientations on the specimen support (Figure a) following incubation in a crystallization Teflon well, coated with a lipid monolayer consisting of phosphatidylcholine and monosialoganglioside. When lying in an end-on orientation, the lectin exhibited a “pentagonal ring” with an outer diameter of 6.7 nm and an inner hollow core of 1.7 nm. A side orientation was also seen, whereby a thickness of 5.8 nm was measured for the lectin. Image processing of 2280 single particles placed in 100 classes (Figure b) led to 3D reconstructions of RSVL (Figure c). Density limited 3D reconstructions showed the lectin to be made of two five-fold symmetrical rings covalently linked between the five subunits that constitute each ring of this homodimer. These results are consistent with sedimentation and preliminary X-ray diffraction analysis on the shape of RSVL and provide the framework for structural verification by 2D electron crystallography.

Characterisation of Type 2N von Willebrand Disease Using Phenotypic and Molecular Techniques

1996 ◽  
Vol 75 (06) ◽  
pp. 959-964 ◽  
Author(s):  
I M Nesbitt ◽  
A C Goodeve ◽  
A M Guilliatt ◽  
M Makris ◽  
F E Preston ◽  
...  
Keyword(s):  
Direct Sequencing ◽  
Von Willebrand Disease ◽  
Molecular Techniques ◽  
Haemophilia A ◽  
Binding Region ◽  
Gene Encoding ◽  
Covalently Linked ◽  
Von Willebrand ◽  
Willebrand Factor

Summaryvon Willebrand factor (vWF) is a multimeric glycoprotein found in plasma non covalently linked to factor VIII (FVIII). Type 2N von Willebrand disease (vWD) is caused by a mutation in the vWF gene that results in vWF with a normal multimeric pattern, but with reduced binding to FVIII.We have utilised methods for the phenotypic and genotypic detection of type 2N vWD. The binding of FVIII to vWF in 69 patients, 36 with type 1 vWD, 32 with mild haemophilia A and one possible haemophilia A carrier with low FVIII levels was studied. Of these, six were found to have reduced binding (five type 1 vWD, one possible haemophilia A carrier), DNA was extracted from these patients and exons 18-23 of the vWF gene encoding the FVIII binding region of vWF were analysed. After direct sequencing and chemical cleavage mismatch detection, a Thr28Met mutation was detected in two unrelated individuals, one of whom appears to be a compound heterozygote for the mutation and a null allele. No mutations were found in the region of the vWF gene encoding the FVIII binding region of vWF in the other four patients

Imine as a Linchpin Approach for Distal C(sp2)–H Functionalization

2020 ◽  
Author(s):  
Sukdev Bag ◽  
Sadhan Jana ◽  
Sukumar Pradhan ◽  
Suman Bhowmick ◽  
Nupur Goswami ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Bond Activation ◽  
Bond Formation ◽  
Ancillary Ligand ◽  
Significant Challenge ◽  
Site Selectivity ◽  
Directing Group ◽  
Covalently Linked ◽  
Complex Organic ◽  
Post Functionalization

<p>Despite the widespread applications of C–H functionalization, controlling site selectivity remains a significant challenge. Covalently attached directing group (DG) served as an ancillary ligand to ensure proximal <i>ortho</i>-, distal <i>meta</i>- and <i>para</i>-C-H functionalization over the last two decades. These covalently linked DGs necessitate two extra steps for a single C–H functionalization: introduction of DG prior to C–H activation and removal of DG post-functionalization. We introduce here a transient directing group for distal C(<i>sp<sup>2</sup></i>)-H functionalization <i>via</i> reversible imine formation. By overruling facile proximal C-H bond activation by imine-<i>N</i> atom, a suitably designed pyrimidine-based transient directing group (TDG) successfully delivered selective distal C-C bond formation. Application of this transient directing group strategy for streamlining the synthesis of complex organic molecules without any necessary pre-functionalization at the distal position has been explored.</p>

Dynamics of Ion Locking in Doubly Polymerized Ionic Liquids

2020 ◽  
Author(s):  
Swati Arora ◽  
Julisa Rozon ◽  
Jennifer Laaser
Keyword(s):  
Dielectric Constant ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Ion Pairs ◽  
Polymer Chains ◽  
Ion Motion ◽  
Charged Species ◽  
Broadband Dielectric Spectroscopy ◽  
Covalently Linked ◽  
Insight Into

<div>In this work, we investigate the dynamics of ion motion in “doubly-polymerized” ionic liquids (DPILs) in which both charged species of an ionic liquid are covalently linked to the same polymer chains. Broadband dielectric spectroscopy is used to characterize these materials over a broad frequency and temperature range, and their behavior is compared to that of conventional “singly-polymerized” ionic liquids (SPILs) in which only one of the charged species is attached to the polymer chains. Polymerization of the DPIL decreases the bulk ionic conductivity by four orders of magnitude relative to both SPILs. The timescales for local ionic rearrangement are similarly found to be approximately four orders of magnitude slower in the DPILs than in the SPILs, and the DPILs also have a lower static dielectric constant. These results suggest that copolymerization of the ionic monomers affects ion motion on both the bulk and the local scales, with ion pairs serving to form strong physical crosslinks between the polymer chains. This study provides quantitative insight into the energetics and timescales of ion motion that drive the phenomenon of “ion locking” currently under investigation for new classes of organic electronics.</div>

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