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Related Concept Videos

Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism01:21

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Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
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In the late 1800s, the revelation that light extended beyond visible wavelengths led to the discovery of X-rays by Wilhelm Roentgen. Recognized as high-energy electromagnetic radiation with short wavelengths, X-rays prompted exploration into their interaction with crystals. Max von Laue proposed in 1912 that the periodic arrangement of atoms, ions, or molecules in crystals would cause them to diffract X-rays, a hypothesis confirmed through experiments with copper sulfate and zinc sulfide...
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Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
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Related Experiment Video

Updated: Apr 21, 2026

PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase
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Solid tryptophan as a pseudoracemate: physicochemical and crystallographic characterization.

Yan Li1, Yuming Zhao, Yan Zhang

  • 1Faculty of Engineering & Applied Science, Memorial University of Newfoundland, St Joh's, NL, Canada.

Chirality
|October 30, 2014
PubMed
Summary
This summary is machine-generated.

Solid tryptophan forms a pseudoracemate, a type of solid solution, across all compositions. This is due to similar crystal structures and interactions between enantiomers, influencing its solid-state properties.

Keywords:
X-ray crystallographyphase diagramracemic modificationsolid solutiontryptophan

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Area of Science:

  • Solid-state chemistry
  • Crystallography
  • Thermodynamics

Background:

  • Tryptophan is an essential amino acid with implications in various biological and chemical processes.
  • Understanding the crystalline behavior of amino acids is crucial for pharmaceutical formulation and material science.
  • The solid-state properties of chiral compounds can significantly differ based on their enantiomeric composition.

Purpose of the Study:

  • To characterize the crystalline nature of solid tryptophan.
  • To determine the solid-state behavior of tryptophan across its entire enantiomeric composition range.
  • To elucidate the factors governing the crystal structure and thermodynamic properties of tryptophan solid solutions.

Main Methods:

  • X-ray single crystal and powder diffraction analyses were employed to determine crystal structures.
  • Differential scanning calorimetry (DSC) was used for thermodynamic characterization.
  • Solid-liquid equilibrium measurements in water/isopropanol solutions were conducted.

Main Results:

  • Tryptophan was unambiguously identified to crystallize as a pseudoracemate (solid solution) over the entire enantiomeric composition range.
  • Thermodynamic investigations confirmed maximum melting behavior consistent with a pseudoracemate.
  • X-ray studies revealed highly similar crystal structures for racemic and enantiomeric tryptophan, dominated by hydrogen bonding.

Conclusions:

  • The formation of a pseudoracemate in tryptophan is attributed to the insignificant difference between homochiral and heterochiral interactions.
  • Tryptophan exhibits continuous solid solution formation, impacting its physical and chemical properties.
  • This study provides fundamental insights into the solid-state behavior of chiral molecules like tryptophan.