Decacationic Pillar[5]arene: A New Scaffold for the Development of 129Xe MRI Imaging Agents.

A decacationic water-soluble pillar[5]arene possessing a nonsolvated hydrophobic core has been designed and synthesized. This supramolecular host is capable of binding xenon, as evidenced by hyperCEST depletion experiments. Fluorescence-based studies also demonstrate that xenon binds into the cavity of the pillararene with an association constant of 4.6 × 103 M-1. These data indicate that the water-soluble pillararene is a potential scaffold for building contrast agents that can be detected by xenon-129 magnetic resonance imaging.

Quantifying biochar content in a field soil with varying organic matter content using a two-temperature loss on ignition method.

While the use of biochar as a soil amendment for agronomic and environmental management is gaining popularity, quantification of biochar in soil is still challenging. The objective of this work was to develop a fast, simple and inexpensive method to quantify biochar content in field soil with varying organic matter content - the two-temperature loss on ignition (LOI) method. In this approach, biochar mass fraction in a biochar-amended soil is computed by measuring the dry mass of biochar/soil mixture after heating sequentially at two temperatures: low temperature (LT), and high temperature (HT). This method requires the LOI profile for pure soil and pure biochar that are representative of soil and biochar in the field. Although the soil LOI profile may vary due to spatial variation in soil organic matter (SOM) content, the method only requires that the relative soil LOI at LT with respect to LOI at HT is uniform because of similarity in SOM chemical composition. In this method, LT and HT are selected such that the maximum difference in LOI exists at these temperatures between pure soil and biochar. The method was tested by quantifying the biochar content in roadway filter strips with and without a wood biochar pyrolyzed at high temperature (550 °C). The estimates of biochar content from the method matched independent measurements for soils with low (-0.23 ±â€¯0.09 CI%, CI = 95% confidence interval, versus actual 0%) and high (3.9 ±â€¯0.3 CI% versus actual 4.0 ±â€¯1.1 CI%) biochar mass fraction. The method is applicable when SOM content is low to moderate (e.g. <15%) and mostly composed of labile organic compounds, and when biochars are pyrolyzed at moderate to high temperatures (i.e. >400 °C) and composed of relatively low ash content (e.g. <30%).

Synthesis of second-generation sansalvamide A derivatives: novel templates as potential antitumor agents.

We report the synthesis of 34 second-generation Sansalvamide A derivatives. San A derivatives have unique anticancer properties and target multiple cancers, including colon, pancreatic, breast, prostate, and melanoma. As novel templates, the derivatives described herein explore the role of stereochemistry, amide bond geometry, transannular hydrogen bonding, and polarity on antitumor potency. Testing the chemotherapeutic activity of these derivatives against multiple cancer cell lines will provide clear structural motifs and identify conformational space that is important for cytotoxicity. The 34 compounds presented are divided into six series, where five series involve the insertion of D-amino acids in conjunction with four structural features at each of the five positions of the macrocycle. The sixth series involves comparison between all L- and all D-amino acid derivatives with N-methyls placed at each position around the macrocyclic core. The four structural features explored in conjunction with D-amino acids include N-methyl amino acids, aromatic amino acids, polar amino acids, and hydrophobic alkyl amino acids.

Synthesis of Sansalvamide A derivatives and their cytotoxicity in the MSS colon cancer cell line HT-29.

We report the synthesis of thirty-six Sansalvamide A derivatives, and their biological activity against colon cancer HT-29 cell line, a microsatellite stable (MSS) colon cancer cell-line. The thirty-six compounds can be divided into three subsets, where the first subset of compounds contains L-amino acids, the second subset contains D-amino acids, and the third subset contains both D- and L-amino acids. Five compounds exhibited excellent inhibitory activity (>75% inhibition). The structure-activity relationship (SAR) of the compounds established that a single D-amino acid in position 2 or 3 gave up to a 10-fold improved cytotoxicity over Sansalvamide A peptide. This work highlights the importance of residues 2 and 3 and the role of D-amino acids in the extraordinary SAR for this compound class.

Synthesis and cytotoxicity of novel sansalvamide A derivatives.

Described are the syntheses of 14 derivatives of the natural product Sansalvamide A, where two are more active against HCT 116 colon cancer cell lines than the natural product. These derivatives were synthesized using a combinatorial-type strategy that permits elucidation of the amino acid role in the cytotoxicity, and they lay the groundwork for development of new anticancer agents. [structure: see text]