A revision of the structure of (bipyridyl-N,N')-dicyanoplatinum(II)

In a previous X-ray crystallographic study of crystals of Pt(bpy)(CN)_2 (bpy = 2,2'-bipyridine) the planar molecules were reported to be exactly eclipsed, stacked directly on top of one another with a spacing of 3.33 Å so as to form a linear Pt· · ·Pt· · ·Pt chain. A reinvestigation shows this structure to be incorrect. The presence of weak intermediate layer lines indicates that the repeat distance along the stacking direction is 6.66 Å rather than 3.33 Å. Successive molecules within the stack are rotated by 180° and the resulting Pt-atom chain is slightly zigzag with a Pt· · ·Pt· · ·Pt angle of 168.6 (1)°. The implications are discussed of the determination and refinement of an apparently satisfactory, although grossly wrong, structure that was based on an incorrect unit cell and an incorrect space group

Emission Spectroscopic Properties of the Red Form of Dichloro(2,2‘-bipyridine)platinum(II). Role of Intermolecular Stacking Interactions

The structure of the red form of Pt(bpy)Cl_2 (bpy = 2,2‘-bipyridine) has been studied by variable-temperature X-ray crystallography. The stack of square-planar Pt(bpy)Cl_2 units in the linear-chain material contracts with decreasing temperature; in the interval between 294 and 20 K, the platinum−platinum distance shortens from 3.449(1) to 3.370(2) Å. Both absorption and emission spectra of the red compound depend strikingly on temperature; as previously found for tetracyanoplatinate salts, the emission maximum red-shifts as the temperature drops (613 nm at 300 K; 651 nm at 10 K), with the peak energy decreasing linearly with the inverse cube of the metal−metal separation

HIV-1 infection and CD4 T cell depletion in the humanized Rag2(-/-)γc(-/- )(RAG-hu) mouse model

BACKGROUND: The currently well-established humanized mouse models, namely the hu-PBL-SCID and SCID-hu systems played an important role in HIV pathogenesis studies. However, despite many notable successes, several limitations still exist. They lack multi-lineage human hematopoiesis and a functional human immune system. These models primarily reflect an acute HIV infection with rapid CD4 T cell loss thus limiting pathogenesis studies to a short-term period. The new humanized Rag2(-/-)γc(-/- )mouse model (RAG-hu) created by intrahepatic injection of CD34 hematopoietic stem cells sustains long-term multi-lineage human hematopoiesis and is capable of mounting immune responses. Thus, this model shows considerable promise to study long-term in vivo HIV infection and pathogenesis. RESULTS: Here we demonstrate that RAG-hu mice produce human cell types permissive to HIV-1 infection and that they can be productively infected by HIV-1 ex vivo. To assess the capacity of these mice to sustain long-term infection in vivo, they were infected by either X4-tropic or R5-tropic HIV-1. Viral infection was assessed by PCR, co-culture, and in situ hybridization. Our results show that both X4 and R5 viruses are capable of infecting RAG-hu mice and that viremia lasts for at least 30 weeks. Moreover, HIV-1 infection leads to CD4 T cell depletion in peripheral blood and thymus, thus mimicking key aspects of HIV-1 pathogenesis. Additionally, a chimeric HIV-1 NL4-3 virus expressing a GFP reporter, although capable of causing viremia, failed to show CD4 T cell depletion possibly due to attenuation. CONCLUSION: The humanized RAG-hu mouse model, characterized by its capacity for sustained multi-lineage human hematopoiesis and immune response, can support productive HIV-1 infection. Both T cell and macrophage tropic HIV-1 strains can cause persistent infection of RAG-hu mice resulting in CD4 T cell loss. Prolonged viremia in the context of CD4 T cell depletion seen in this model mirrors the main features of HIV infection in the human. Thus, the RAG-hu mouse model of HIV-1 infection shows great promise for future in vivo pathogenesis studies, evaluation of new drug treatments, vaccines and novel gene therapy strategies

Procedural confidence in hospital based practitioners: implications for the training and practice of doctors at all grades

<p>Abstract</p> <p>Background</p> <p>Medical doctors routinely undertake a number of practical procedures and these should be performed competently. The UK Postgraduate Medical Education and Training Board (PMETB) curriculum lists the procedures trainees should be competent in. We aimed to describe medical practitioner's confidence in their procedural skills, and to define which practical procedures are important in current medical practice.</p> <p>Methods</p> <p>A cross sectional observational study was performed measuring procedural confidence in 181 hospital practitioners at all grades from 2 centres in East Anglia, England.</p> <p>Results</p> <p>Both trainees and consultants provide significant service provision. SpR level doctors perform the widest range and the highest median number of procedures per year. Most consultants perform few if any procedures, however some perform a narrow range at high volume. Cumulative confidence for the procedures tested peaks in the SpR grade. Five key procedures (central line insertion, lumbar puncture, pleural aspiration, ascitic aspiration, and intercostal drain insertion) are the most commonly performed, are seen as important generic skills, and correspond to the total number of procedures for which confidence can be maintained. Key determinants of confidence are gender, number of procedures performed in the previous year and total number of procedures performed.</p> <p>Conclusion</p> <p>The highest volume of service requirement is for six procedures. The procedural confidence is dependent upon gender, number of procedures performed in the previous year and total number of procedures performed. This has implications for those designing the training curriculum and with regards the move to shorten the duration of training.</p

A revision of the structure of (bipyridyl-N,N')-dicyanoplatinum(II)

In a previous X-ray crystallographic study of crystals of Pt(bpy)(CN)_2 (bpy = 2,2'-bipyridine) the planar molecules were reported to be exactly eclipsed, stacked directly on top of one another with a spacing of 3.33 Å so as to form a linear Pt· · ·Pt· · ·Pt chain. A reinvestigation shows this structure to be incorrect. The presence of weak intermediate layer lines indicates that the repeat distance along the stacking direction is 6.66 Å rather than 3.33 Å. Successive molecules within the stack are rotated by 180° and the resulting Pt-atom chain is slightly zigzag with a Pt· · ·Pt· · ·Pt angle of 168.6 (1)°. The implications are discussed of the determination and refinement of an apparently satisfactory, although grossly wrong, structure that was based on an incorrect unit cell and an incorrect space group

Emission Spectroscopic Properties of the Red Form of Dichloro(2,2‘-bipyridine)platinum(II). Role of Intermolecular Stacking Interactions

The structure of the red form of Pt(bpy)Cl_2 (bpy = 2,2‘-bipyridine) has been studied by variable-temperature X-ray crystallography. The stack of square-planar Pt(bpy)Cl_2 units in the linear-chain material contracts with decreasing temperature; in the interval between 294 and 20 K, the platinum−platinum distance shortens from 3.449(1) to 3.370(2) Å. Both absorption and emission spectra of the red compound depend strikingly on temperature; as previously found for tetracyanoplatinate salts, the emission maximum red-shifts as the temperature drops (613 nm at 300 K; 651 nm at 10 K), with the peak energy decreasing linearly with the inverse cube of the metal−metal separation

Linear-Chain Structures of Platinum(II) Diimine Complexes

The structures of three linear-chain platinum(II) diimine complexes have been determined [Pt···Pt, Å]:  Pt(bpm)Cl_2·0.5(nmp) (3) [3.411(1), 3.371(1)], Pt(phen)(CN)_2 (6) [3.338(1), 3.332(1)], and Pt(bpy)(NCS)_2 (7) [3.299(2)] (bpm = 2,2‘-bipyrimidine, phen = 1,10-phenanthroline, bpy = 2,2‘-bipyridine, nmp = 1-methyl-2-pyrrolidinone). The Pt···Pt distances in these and in seven related compounds range from 3.24 to 3.49 Å. While we find evidence of interligand interactions influencing these structures, the Pt···Pt bonds are the most important of the stacking forces. The metal−metal distances are generally consistent with an electronic structural model in which σ-donor/π-acceptor ligands strengthen Pt···Pt bonding interactions (for example, the Pt···Pt distances in 3 are 0.04 and 0.08 Å shorter than in the bpy analogue). We have also found that the yellow form of Pt(dmbpy)(NCO)_2 (1b) (4,4‘-dimethyl-2,2‘-bipyridine) has a columnar structure; however, in contrast to the linear-chain form (1), which is orange, the Pt atoms are well separated (>4.9 Å). Interestingly, the yellow form is 7% denser than the orange form; this result is consistent with the concept that directed intermolecular interactions give rise to lower density polymorphs. Crystal data:  (3) monoclinic, C2/m (No. 12), a = 12.668(4) Å, b = 15.618(6) Å, c = 6.704(3) Å, β = 93.43(3)°, Z = 4; (6) orthorhombic, Pbca (No. 61), a = 38.731(13) Å, b = 18.569(3) Å, c = 6.628(1) Å, Z = 16; (7) orthorhombic, Pbcm (No. 57), a = 10.349(3) Å, b = 19.927(5) Å, c = 6.572(3) Å, Z = 4; (1b) monoclinic, C2/c (No. 15), a = 17.313(4) Å, b = 12.263(3) Å, c = 14.291(4) Å, β = 114.00(2)°, Z = 8

Bostonia: The Boston University Alumni Magazine. Volume 12

Founded in 1900, Bostonia magazine is Boston University’s main alumni publication