N-Cyclohexyl-3-aminopropanesulfonic acid
[CAS# 1135-40-6]

Identification

• Classification: Chemical reagent >> Organic reagent >> Sulfonic acid / sulfinic acid
• Name: N-Cyclohexyl-3-aminopropanesulfonic acid
• Synonyms: 3-(Cyclohexylamino)-1-propanesulfonic acid; CAPS
• Molecular Formula: C₉H₁₉NO₃S
• Molecular Weight: 221.31
• CAS Registry Number: 1135-40-6
• EC Number: 214-492-1
• SMILES: C1CCC(CC1)NCCCS(=O)(=O)O

Properties

• Melting point: 324 °C
• Water solubility: 9 g/100 mL (20 °C)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	2	H300
Acute toxicity	Acute Tox.	4	H312

Discovery and Applications

N-Cyclohexyl-3-aminopropanesulfonic acid, commonly known as CAPS, was discovered during the search for effective biological buffers. CAPS is part of the Good buffers, introduced by Norman Good and colleagues in the 1960s. These buffers were designed to provide stable pH conditions necessary for biological and biochemical research. CAPS has a zwitterionic nature and the ability to maintain a stable pH, making it a valuable tool for scientists.

The molecular formula of CAPS is C9H19NO3S. It features a cyclohexyl group attached to 3-aminopropanesulfonic acid, combining a hydrophobic part and a highly water-soluble sulfonic acid group. CAPS has a pKa of 10.4, making it suitable for buffering in the pH range of 9.7 to 11.1. This property allows CAPS to be used in applications that require an alkaline environment, distinguishing it from many other buffers.

CAPS is widely used in biochemical and molecular biology research, especially in experiments that require a stable alkaline pH. It is an excellent choice for maintaining pH during enzyme reactions and protein purification. Its stability and minimal interference with biochemical reactions make it suitable for high-precision experiments.

CAPS is frequently used as an electrophoresis buffer, including SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and capillary electrophoresis. Its buffering capacity ensures consistent separation of proteins and nucleic acids, providing accurate results in molecular weight and conformational analysis.

During protein purification, CAPS helps maintain the pH of the solution, ensuring that the protein remains in its native, functional state. This is critical for techniques such as ion exchange chromatography and affinity chromatography, as pH stability is key to the effective separation and purification of proteins.

CAPS is used to formulate diagnostic reagents, especially those that require a stable alkaline pH. Its nontoxic nature and compatibility with a variety of biological systems make it an ideal ingredient in diagnostic kits and assays.

In addition to research laboratories, CAPS can also be used in industrial processes, especially in the manufacture of pharmaceuticals and biotech products. Its buffering capacity and stability under alkaline conditions make it valuable in large-scale production processes.

References

2024. Amphiphilic self-assembling peptides: formulation and elucidation of functional nanostructures for imaging and smart drug delivery. Analytical and Bioanalytical Chemistry.
DOI: 10.1007/s00216-024-05650-w

2023. Chemical-Biology and Metabolomics Studies in Phage-Host Interactions. Advances in Experimental Medicine and Biology.
DOI: 10.1007/978-3-031-41741-2_4

2023. Fibril formation and ordering of disordered FUS LC driven by hydrophobic interactions. Nature Chemistry.
DOI: 10.1038/s41557-023-01221-1