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Related Concept Videos

Chirality at Nitrogen, Phosphorus, and Sulfur02:30

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Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
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The naming of enantiomers employs the Cahn–Ingold–Prelog rules that involve assigning priorities to different substituent groups at a chiral center. Each enantiomer, being a distinct molecule, is assigned a unique name by the Cahn–Ingold–Prelog (CIP) rules, also called the R–S system. The prefix R- or S- attached to the chiral centers in an enantiomer is dependent on the spatial arrangement of the four substituents on the chiral center. The R–S system...
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A racemic mixture, or racemate, is an equimolar mixture of enantiomers of a molecule that can be separated using their unique interaction with chiral molecules or media. Racemic mixtures are denoted by the (±)- prefix. This ‘optical rotation descriptor’ applies to the whole solution of a racemic mixture rather than a specific stereoisomer. Enantiomers typically have the same physical and chemical properties. Hence, they are not easily separable. However, enantiomers can exhibit...
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In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
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It is essential to understand the difference between chiral and achiral interactions and the implications thereof in optical activity and their applications. Just as our feet, which are chiral, interact uniquely with chiral objects, such as a pair of shoes, but identically with achiral socks, enantiomers of a molecule exhibit different properties only when they interact with other chiral media. An example of a significant implication from this facet is the phenomenon known as optical activity,...
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Updated: Sep 2, 2025

Quantitative and Qualitative Method for Sphingomyelin by LC-MS Using Two Stable Isotopically Labeled Sphingomyelin Species
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Nontoxic Enantiomeric Reference Materials for Saxitoxins.

Ryuichi Watanabe1, Yuka Takayanagi2, Osamu Chiba3

  • 1Fisheries Technology Institute, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan.

Analytical Chemistry
|August 8, 2022
PubMed
Summary

Saxitoxin (STX) monitoring in shellfish is challenging due to its chemical warfare agent status. Nontoxic antipodal STXs (ent-STXs) offer a safe alternative for calibration standards, reducing reliance on hazardous STX.

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Area of Science:

  • Marine Biology
  • Analytical Chemistry
  • Toxicology

Background:

  • Saxitoxin (STX) is a potent neurotoxin found in shellfish, posing a public health risk.
  • Current analytical methods for STX require calibration standards, but STX's classification as a chemical warfare agent complicates international trade and accessibility.

Purpose of the Study:

  • To develop a method for preparing and utilizing nontoxic saxitoxin analogues as calibration standards.
  • To circumvent restrictions imposed by the Chemical Weapons Convention for STX analysis.

Main Methods:

  • Synthesis of unnatural antipodal saxitoxins (ent-STXs) with identical physicochemical properties to natural STXs.
  • Validation of ent-STXs as safe and effective reference materials for STX quantification.

Main Results:

  • Nontoxic ent-STXs were successfully prepared and demonstrated to possess equivalent physicochemical properties to natural STXs.
  • ent-STXs can be safely used as alternative calibration standards in routine shellfish monitoring programs.

Conclusions:

  • The use of ent-STXs provides a viable solution for overcoming regulatory hurdles in STX analysis.
  • This approach facilitates accurate shellfish monitoring and reduces the need for hazardous STX standards.