Discrimination of Scrophularia spp. according to geographic origin with HPLC-DAD combined with multivariate analysis

Discrimination of Scrophularia spp. according to the geographic origin was tried in the present study using HPLC-DAD combined with multivariate analysis techniques. Five active constituents, angoroside C, harpagoside, 8-O-(E-p-methoxycinnamoyl)harpagide, E-cinnamic acid and E-p-methoxycinnamic acid, in forty four Scrophularia samples were simultaneously determined using HPLC-DAD. A principal component analysis of the content measurements clustered the samples according to their geographic origins, Andong, Uisung and China. A partial least squares-discrimination analysis was subsequently developed for the effective classification of the samples. This model showed comparatively good prediction ability for samples from Andong or China. The proposed method shows an efficient strategy for quality control of Scrophularia spp.     

Self-assembled peptide architecture with a tooth shape: folding into shape

Molecular self-assembly is the spontaneous association of molecules into structured aggregates by which nature builds complex functional systems. While numerous examples have focused on 2D self-assembly to understand the underlying mechanism and mimic this process to create artificial nano- and microstructures, limited progress has been made toward 3D self-assembly on the molecular level. Here we show that a helical β-peptide foldamer, an artificial protein fragment, with well-defined secondary structure self-assembles to form an unprecedented 3D molecular architecture with a molar tooth shape in a controlled manner in aqueous solution. Powder X-ray diffraction analysis, combined with global optimization and Rietveld refinement, allowed us to propose its molecular arrangement. We found that four individual left-handed helical monomers constitute a right-handed superhelix in a unit cell of the assembly, similar to that found in the supercoiled structure of collagen.     

Investment and financing decisions in the presence of time-to-build

We study a firm’s optimal decisions on investment, default, and financing when the amount of time and the running costs for project completion are uncertain. In the presence of time-to-build, a firm makes conservative investment and financing decisions; investment is delayed, and the optimal leverage ratio is inverted U-shaped with respect to the size of the lag. Although equity holders can choose to default before the project has been completed, the default probability in the presence of time-to-build is lower than that in the absence of a lag in most cases because of the conservative investment and financing decisions. Given the lower default probability, equity holders may benefit more from debt financing in the presence of time-to-build than they would in the absence of a lag. When firms can shorten their expected time-to-build by bearing more costs, unlevered firms strive to reduce the lag more than optimally levered firms do. However, highly levered firms utilize more resources to reduce the lag than all-equity firms do because equity holders are more concerned about the possibility of default before the project’s completion.     

Rapid identification and evaluation of antioxidant compounds from extracts of Petasites japonicus by hyphenated-HPLC techniques

Gradient HPLC coupled to Diode Array Detector (DAD), MS/MS and NMR was applied to the rapid structure determination of major compounds of methanol extracts from leaves and roots of Petasites japonicus. The relative antioxidant capacities of the compounds were evaluated by an HPLC system with post-column on-line antioxidant detection based on 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid radical scavenging. Six compounds were successfully separated on a reverse-phase C(18) column and were identified as 5-caffeoylquinic acid (5-CQA), fukinolic acid (FA), 3,5-di-O-caffeoylquinic acid (3,5-DCQA), quercetin-3-O-(6″-acetyl)-β-glucopyranoside (QAG), 4,5-di-O-caffeoylquinic acid (4,5-DCQA) and kaempferol-3-O-(6″-acetyl)-β-glucopyranoside (KAG) by MS/MS and (1)H NMR data. Among these compounds, those containing a caffeoyl moiety (5-CQA, FA, 3,5- and 4,5-DCQA) showed relatively strong radical scavenging capacity, with 3,5-DCQA having the greatest radical scavenging capacity in leaf (23.09% of total antioxidant capacity) and root (26.47%) extracts. The relative radical scavenging portion of QAG was only 3.41% in the leaves and KAG did not show any radical scavenging activity. These results demonstrate that the hyphenated HPLC techniques can be successfully applied to rapidly identify structures and evaluate antioxidant activities without prior purification of compounds from plant tissues of P. japonicus.     

A strategy to enhance the binding affinity of fluorophore-aptamer pairs for RNA tagging with neomycin conjugation

Fluorogenic sulforhodamine-neomycin conjugates have been designed and synthesized for RNA tagging. Conjugates were fluorescently activated by binding to RNA aptamers and exhibited greater than 250-400 fold enhancement in binding affinity relative to corresponding unconjugated fluorophores.     

Cyanido-bridged one-dimensional systems assembled from [ReIVCl4(CN)2]2? and [MII(cyclam)]2+ (M = Ni, Cu) precursors

Three new cyanido-bridged heterometallic Re^IVNi^II and Re^IVCu^II one-dimensional systems were synthesized and extensively characterized both structurally and magnetically. Single-crystal X-ray diffraction analysis revealed that these compounds display a common topology, with chains composed of alternating [Re^IVCl₄(CN)₂]^2? and [M^II(cyclam)]²⁺ (M = Ni in 1, Cu in 2) or [Cu^II(N,N??-dimethylcyclam)]²⁺ (in 3) building units. Two different chain orientations with a tilt angle of ca. 51° to 55° are present in the crystal packing of these compounds. The magnetic susceptibility measurements suggest the presence of intrachain ferromagnetic interactions between the S = 3/2 Re^IV centers and the 3d metal ions: S = 1 Ni^II or S = 1/2 Cu^II. At low temperature, a three-dimensional ordered magnetic phase induced by interchain antiferromagnetic interactions (antiferromagnetic for 1 and 2; canted antiferromagnetic for 3) is detected for the three compounds.     

Stereoselective synthesis of novel pyrazole derivatives using tert-butansulfonamide as a chiral auxiliary

A novel chiral pyrazole derivative was developed by our research program as a potent PDE4 inhibitor for the treatment of anti-inflammatory diseases, such as asthma and chronic obstructive pulmonary disease. The asymmetric synthesis of the inhibitors carrying the pyrazole moiety, including nitrogen directly bonded to a chiral center, through a novel approach is disclosed. The key steps of the synthetic sequence begin with the preparation of chiral toluenesulfinyl imine by the condensation of (R)- and (S)-tert-butanesulfinamide with an aldehyde. Next, a corresponding chiral amine synthesis by a stereoselective addition reaction of 4-picolyl lithium to the chiral toluenesulfinyl imine is performed, followed by desulfination. The preparation of the cis-type enaminone from the addition of the enaminone to the corresponding chiral amine is then accomplished, with further transformation into the pyrazole derivatives through the amination of the enaminones and subsequent dehydro-cyclization. A total of 8 steps are completed to produce a 5.5% yield (100% ee).     

p190RhoGAP and Rap-dependent RhoGAP (ARAP3) inactivate RhoA in response to nerve growth factor leading to neurite outgrowth from PC12 cells

Rat pheochromocytoma (PC12) cells have been used to investigate neurite outgrowth. Nerve growth factor (NGF) has been well known to induce neurite outgrowth from PC12 cells. RhoA belongs to Ras-related small GTP-binding proteins, which regulate a variety of cellular processes, including cell morphology alteration, actin dynamics, and cell migration. NGF suppressed GTP-RhoA levels after 12 h in PC12 cells and was consistently required for a long time to induce neurite outgrowth. Constitutively active (CA)-RhoA suppressed neurite outgrowth from PC12 cells in response to NGF, whereas dominant-negative (DN)-RhoA stimulated it, suggesting that RhoA inactivation is essential for neurite outgrowth. Here, we investigated the mechanism of RhoA inactivation. DN-p190RhoGAP abrogated neurite outgrowth, whereas wild-type (WT)-p190RhoGAP and WT-Src synergistically stimulated it along with accelerating RhoA inactivation, suggesting that p190RhoGAP, which can be activated by Src, is a major component in inhibiting RhoA in response to NGF in PC12 cells. Contrary to RhoA, Rap1 was activated by NGF, and DN-Rap1 suppressed neurite outgrowth, suggesting that Rap1 is also essential for neurite outgrowth. RhoA was co-immunoprecipitated with Rap1, suggesting that Rap1 interacts with RhoA. Furthermore, a DN-Rap-dependent RhoGAP (ARAP3) prevented RhoA inactivation, abolishing neurite formation from PC12 cells in response to NGF. These results suggest that NGF activates Rap1, which, in turn, up-regulates ARAP3 leading to RhoA inactivation and neurite outgrowth from PC12 cells. Taken together, p190RhoGAP and ARAP3 seem to be two main factors inhibiting RhoA activity during neurite outgrowth in PC12 cells in response to NGF.