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Crystal Field Theory - Octahedral Complexes

Crystal Field Theory - Octahedral Complexes

Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
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Porin Insertion in the Outer Mitochondrial Membrane

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Related Experiment Video

Updated: Jul 24, 2026

In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa

In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa

Published on: February 17, 2014

Crystal structures explain functional properties of two E. coli porins.

S W Cowan¹, T Schirmer, G Rummel

¹Department of Structural Biology, University of Basel, Switzerland.

|August 27, 1992

Summary

Bacterial outer membrane porins, which facilitate molecule diffusion, form trimers with beta-barrel structures. Their pore constrictions, influenced by charged loops, determine ion selectivity and explain mutation effects.

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In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa

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From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins

From Constructs to Crystals – Towards Structure Determination of β-barrel Outer Membrane Proteins

Published on: July 4, 2016

Area of Science:

Structural biology
Microbiology
Biophysics

Background:

Porins are essential outer membrane proteins in Gram-negative bacteria.
They form aqueous channels facilitating the transport of small hydrophilic molecules.
Understanding porin structure-function relationships is crucial for comprehending bacterial physiology.

Purpose of the Study:

To elucidate the molecular mechanisms underlying porin function.
To explain the structural basis of ion selectivity in porin channels.
To correlate structural findings with known functional characteristics and mutations.

Main Methods:

X-ray crystallography was used to determine the structures of matrix porin and phosphoporin.
Analysis of the 16-stranded anti-parallel beta-barrel architecture.
Investigation of the role of internal loops in channel constriction and ion selectivity.

Main Results:

Crystal structures revealed porins as trimers of identical subunits.
Each subunit features a 16-stranded beta-barrel forming a channel.
A long internal loop creates a constriction, with charge distribution governing ion selectivity.

Conclusions:

The determined structures provide a molecular basis for porin function.
Structural insights explain observed ion selectivity and the impact of mutations.
This work enhances understanding of transport across the Gram-negative bacterial outer membrane.