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Basicity of Aromatic Amines

Basicity of Aromatic Amines

The basicity of aromatic amines is much weaker than that of aliphatic amines due to the involvement of the lone pair of electrons over the N atom in resonance with the aryl rings. Generally, the electron-donating ability of any substituents on the aryl ring of aromatic amines increases the basicity of the amine by increasing electron density, and hence the availability of lone pair on the nitrogen. On the other hand, electron-withdrawing functional groups on the aryl ring of amines decrease the...

Basicity of Heterocyclic Aromatic Amines

Basicity of Heterocyclic Aromatic Amines

Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).

Urea Cycle

Urea Cycle

The urea cycle describes how liver cells convert ammonia to urea. Ammonia is a toxic waste product of protein catabolism. Land animals must convert ammonia into the less toxic urea which can be safely eliminated by the kidneys through urine. Marine animals excrete ammonia directly, and the surrounding water dilutes the ammonia to safe levels.

Physical Properties of Amines

Physical Properties of Amines

Amines with low molecular weight are usually gaseous at room temperature, while those with high molecular weight are liquid or solids in nature. Usually, low molecular weight amines have a rotten fish-like smell. Diamines typically have a pungent smell. For instance, cadaverine and putrescine, depicted in Figure 1, are two molecules responsible for decaying tissue.

Amines: Introduction

Amines: Introduction

Amines are organic derivatives of ammonia. They are formed by replacing one or more ammonia protons with alkyl or aryl groups. Depending upon the number of organyl groups bonded to nitrogen, amines are classified as primary, secondary, or tertiary. Primary amines have one organyl group attached to the nitrogen atom, while secondary and tertiary amines have two and three organyl groups attached to the nitrogen atom, respectively.

Structure of Amines

Structure of Amines

The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are...

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Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions

Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions

Published on: April 4, 2014

Urea-aromatic interactions in biology.

Shampa Raghunathan¹, Tanashree Jaganade¹, U Deva Priyakumar²

¹Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad, 500032, India.

Biophysical Reviews

|February 19, 2020

Summary

This summary is machine-generated.

Urea significantly impacts biomolecule stability, particularly through hydrophobic interactions. This review explores urea

Keywords:

Amino acids Aromatic DNA Molecular dynamics simulations Nucleic acids QM calculations RNA Stacking interactions Urea Urea transporter

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Method for Efficient Refolding and Purification of Chemoreceptor Ligand Binding Domain

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Last Updated: Dec 28, 2025

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Method for Efficient Refolding and Purification of Chemoreceptor Ligand Binding Domain

Method for Efficient Refolding and Purification of Chemoreceptor Ligand Binding Domain

Published on: December 12, 2017

Area of Science:

Biochemistry
Chemical Physics
Molecular Biology

Background:

Noncovalent interactions, especially hydrophobic interactions, are crucial for biomolecular structure and function.
Urea, a common biological osmolyte, is known to modulate the stability of proteins and nucleic acids.
Understanding urea's effects is vital for comprehending biological processes and developing therapeutic strategies.

Purpose of the Study:

To review the multifaceted roles of urea in biological systems.
To highlight the significance of hydrophobic interactions in urea's effects on biomolecules.
To synthesize current experimental and theoretical insights into urea's molecular mechanisms.

Main Methods:

Review of experimental studies focusing on thermodynamics and kinetics.
Analysis of theoretical modeling using force fields and quantum mechanics.
Examination of molecular-level mechanistic details.

Main Results:

Urea facilitates protein and RNA unfolding.
Urea interacts with damaged DNA lesions.
Urea transport through membrane proteins is investigated.
Urea-aromatic interactions are critical in protein-ligand binding.

Conclusions:

Urea's influence on biomolecular stability is profound and context-dependent.
Hydrophobic interactions involving urea are central to its biological effects.
Further research combining experimental and theoretical approaches is warranted.