Label-free SERS characterization of snake venoms by exploring the cysteine environs with bone-shaped gold nanoparticles.

Identification of snake venoms is a vital step in the treatment of fatal snakebites. In this study, we use the gold-thiolate interaction between a cysteine residue and gold nanoparticles to establish a SERS method for the differentiation of the venoms of Trimeresurus stejnegeri and Bungarus multicinctus. We confirm the preference of gold nanoparticles over silver for the SERS study of snake venoms by a binding experiment that also functions to differentiate the two venom samples by colorimetry and UV-vis spectroscopy. We report the SERS spectra of Trimeresurus stejnegeri and Bungarus multicinctus venoms for the first time. The spectra display distinct SERS signatures of the snake venoms on bone-shaped gold nanoparticles made with a house recipe. These signatures correlate to selected segments of the venom proteins due to the anchoring effect of the gold-cysteine bond. The method is quick as it accomplishes in situ isolation of the structure of interest to avoid tedious purification of the samples. The location of the interactive cysteine residue makes a novel characteristic of proteins in general.

The chemical aspects of Raman spectroscopy: Statistical structure-spectrum relationship in the analyses of bioflavonoids.

Raman spectroscopy has been accepted as a useful tool for the characterization of natural products. However, to identify a specific compound in a mixture sample of natural products using Raman spectra alone is highly challenging if not impossible. We demonstrated an effective solution to such issues using a method combining statistical Raman spectroscopy and Mass spectrometry. The method was validated with a successful application to the identification of the major anthocyanin components in a purple yam (Dioscorea purpurea) extract. Of particular interest is that statistical grouping of the bioflavonoid standards that formed the database of this study was found to correspond closely to the conventional chemical classification. An initial theory on the chemical aspects of Raman spectroscopy pertaining to the connectivity of Raman-active functional groups in bioflavonoids was developed based on the statistical correlation between chemical classification and Raman spectroscopy.

Synthesis and protein kinase inhibitory activity of balanol analogues with modified benzophenone subunits.

A series of analogues of the protein kinase C (PKC) inhibitory natural product balanol which bear modified benzophenone subunits are described. The analogues were designed with the goal of uncovering structure-activity features that could be used in the development of PKC inhibitors with a reduced polar character compared to balanol itself. The results of these studies suggest that most of the benzophenone features found in the natural product are important for obtaining potent PKC inhibitory compounds. However, several modifications were found to lead to selective inhibitors of the related enzyme protein kinase A (PKA), and several specific modifications to the polar structural elements of the benzophenone were found to provide potent PKC inhibitors. In particular, it was found that replacement of the benzophenone carboxylate with bioisosteric equivalents could lead to potent analogues. Further, a tolerance for lipophilic substituents on the terminal benzophenone ring was uncovered. These results are discussed in light of recently available structural information for PKA.