[(2,3-O-Isopropylidene-5-O-(triphenylmethyl)-α-D-ribofuranosyl]-triphenylstannane

The synthesis, IR, MS, solution and solid state NMR spectra and X-ray structure of (2,3-O-isopropylidene-5-O-(triphenylmethyl)--D-ribofuranosyl]triphenylstannane 1 (R₃Sn) are reported. Compound, 1 (R₃Sn) crystallizes in the orthorhombic space group C222₁ (Z = 8), with a = 8.935(4), b = 17.058(7), c = 47.94(5)Å. There are two short tin–oxygen separations, at 3.030(7) [involving O4, on an alpha carbon] and 3.094(7) Å [involving O2, on a beta carbon]. Only the O4 atom is considered to form a weak and additional bond to tin; this results in a deviation of the geometry at tin toward trigonal bypramid from tetrahedral, with O4 and C34 in the axial sites [C34– Sn–O4=152.3(3)°]. The conformation of the ribofuranosyl ring in the solid state is E _o [P, the phase angle of pseudorotation, = 268.4(9)° and _max , the puckering amplitude, = 38.0(6)°], while the isopropylidene ring conformation is between the envelope form, E _C6, and the twist form, ^O3 T _C6 [P = 46.5(10)° and _max = 36.9(6)°]. In solution, the ribofuranosyl ring adopts a conformation between E _o and ¹ T _o.     

O-[(Triorganostannyl)methyl] derivatives of 1,2-O-isopropylidene-α-D-xylofuranose

The synthesis, mass, IR and NMR spectra of 3-O-benzyl-1,2-O-isopropylidene-5-O-[(triphenylstannyl)methyl]--D-xylofuranose (9) and 1,2-O-isopropylidene-3-O-(R₃SnCH₂)-5-O-triphenylmethyl--D-xylofuranose (10, R=Bu or Ph) are reported, as is the X-ray structure of10 (R=Ph). Compound10 (R=Ph), crystallizes in the orthorhombic space groupP2₁2₁2₁ (Z=4), witha=11.006(4) Å,b=17.096(6) Å,c=21.164(7) Å. The conformation of the furanose ring in solid10 (R=Ph) is a 8218 mixture of the envelope (E₄) and twist (³T₄) forms: the isopropylidene ring conformation is similarly a mixture of envelope and twist forms, with the former dominant. On dissolution, the furanose ring of10 (R=Ph) undergoes a conformation change, with the³T₂ conformation becoming the major form. The tin center in10 is four-coordinate and has a tetrahedral geometry.     

Orientational disorder in 4‐chloronitrobenzene

The crystal structure of 4‐chloronitrobenzene, C₆H₄ClNO₂, a material that exhibits disorder in the solid state, is re‐examined using multiple‐temperature single‐crystal X‐ray diffraction. Our results show a marked improvement on previous crystal structure determinations and our comprehensive multiple temperature measurements help to rationalize the structural anomalies. 4‐Chloronitrobenzene exhibits twofold orientational disorder of the NO₂/Cl substituents, with the molecule lying across an inversion centre. There is also evidence of large thermal motion, which exists at all temperatures and reflects the presence of significant disorder in this material. The nitro group shows possible libration, with one O atom exhibiting larger thermal motion than the other across the whole temperature range. This is explained by a difference in hydrogen‐bonding environment.     

Biocatalytically oligomerized epicatechin with potent and specific anti-proliferative activity for human breast cancer cells

Catechins, naturally occurring flavonoids derived from wine and green tea, are known to exhibit multiple health benefits. Epigallocatechin gallate (EGCG) is one of the most widely investigated catechins, but its efficacy in cancer therapy is still inconsistent and limited. The poor stability of EGCG has contributed to the disparity in the reported anti-cancer activity and other beneficial properties. Here we report an innovative enzymatic strategy for the oligomerization of catechins (specifically epicatechin) that yields stable, water-soluble oligomerized epicatechins with enhanced and highly specific anti-proliferative activity for human breast cancer cells. This one-pot oxidative oligomerization is carried out in ambient conditions using Horseradish Peroxidase (HRP) as a catalyst yielding water-soluble oligo(epicatechins). The oligomerized epicatechins obtained exhibit excellent growth inhibitory effects against human breast cancer cells with greater specificity towards growth-inhibiting cancer cells as opposed to normal cells, achieving a high therapeutic differential. Our studies indicate that water-soluble oligomeric epicatechins surpass EGCG in stability, selectivity and efficacy at lower doses.     

Non-fouling microfluidic chip produced by radio frequency tetraglyme plasma deposition

This Technical Note presents the direct surface modification of a glass/PTFE hybrid microfluidic chip, via radio frequency glow discharge plasma polymerisation of tetraethlylene glycol dimethylether (tetraglyme), to produce hydrophilic, non-fouling, PEO-like surfaces. We use several techniques including X-ray photoelectron spectroscopy (XPS), direct enzyme-linked immunosorbent assays (ELISA) and immunofluorescent imaging to investigate the channel coatings. Our results indicate the successful deposition of a PEO-like coating onto microchannel surfaces that has both solution and shelf stability (>3 months) and is capable of preventing fibrinogen adsorption to the microchannel surfaces.     

Synthesis and characterization of immobilized PAMAM dendrons

This communication describes the synthesis and characterization of immobilized PAMAM dendrons onto a surface modified silicon wafer substrate (functionalized using plasma polymerized PAA) using a "growing from" strategy.     

Ultrafast excited-state electron transfer at an organic liquid/aqueous interface

Ultrafast excited-state electron transfer has been monitored at the liquid/liquid interface for the first time. Second harmonic generation (SHG) pump/probe measurements monitored the electron transfer (ET) occurring between photoexcited coumarin 314 (C314) acceptor and dimethylaniline (DMA) donor molecules. In the treatment of this problem, translational diffusion of solute molecules can be neglected since the donor DMA is one of the liquid phases of the interface. The dynamics of excited-state C314 at early times are characterized by two components with exponential time constants of 362 +/- 60 fs and 14 +/- 2 ps. The 362 fs decay is attributed to the solvation of the excited-state C314, and the 14 ps to the ET from donor to acceptor. We are able to provide conclusive evidence that the 14 ps component is the ET step by monitoring the formation of the radical DMA cation. The formation time is 16 ps in agreement with the 14 ps decay of C314*. The recombination dynamics of DMA+ plus C314- was determined to be 163 ps from the observation of the DMA+ SHG signal.     

Tripeptide self-assembled hydrogels: unexpected twists of chirality

Change of chirality of the first N-terminal amino acid of tripeptides VFF and FFV from l to d results in self-assembled hydrogels at physiological pH from non-assembling l-analogues. Interestingly, changing the chirality of F yields very different nanostructures; nanotapes are observed for (D)VFF, twisted fibers for (D)FFV.     

Nuclear magnetic resonance spectroscopy of rat ventricles following chronic hypoxia: A model of right ventricular hypertrophy

Nuclear magnetic resonance spectroscopy was used to study the effect of chronic hypoxia on both right (RV) and left ventricular and septal (LV + S) muscle. Rats in the hypoxic group, kept in a hypobaric chamber at $\text{1}\text{2}$ atm pressure for 2 weeks, developed right, but not left, ventricular hypertrophy (p < 0.001). Tissues were studied within 2.5 h of return to air. T₁ and T₂ relaxation times of RV, LV + S and thigh muscle (Th) from hypoxic and control rats were compared. The T₂ value distinguished hypoxic from control RV (p < 0.002), but not hypoxic from control LV + S or Th, indicating that the change in relaxation time reflects cellular hypertrophy, and not hypoxemia. For hypoxic rats only the T₂ value distinguished each muscle type: RV from LV + S (p < 0.009), RV from Th (p < 0.001) and LV + S from Th (p < 0001). The T₁ value did not identify either the hypoxic or control group or the type of muscle. Percent water content was similar for all tissues. For hypoxic RV, T₂ correlated with the percent water content (r = 0.89; p < 0.01). The sensitivity of T₂ to the cellular changes associated with hypoxic RV hypertrophy could provide a means of detecting right ventricular hypertrophy.