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Related Concept Videos

Colors and Magnetism03:02

Colors and Magnetism

Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Pigmentation01:19

Pigmentation

The color of the skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. The melanin is transferred to the keratinocytes via melanosomes.
Melanin occurs in two primary forms: eumelanin that provides black and brown pigment and pheomelanin that provides red color. Dark-skinned individuals produce more melanin than those with pale...
Paramagnetism01:30

Paramagnetism

Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
Calmodulin-dependent Signaling01:16

Calmodulin-dependent Signaling

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Potential Due to a Magnetized Object01:24

Potential Due to a Magnetized Object

Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
Other Unique Bacteria01:18

Other Unique Bacteria

Magnetic bacteria exhibit a directed movement called magnetotaxis, driven by structures called magnetosomes. These magnetosomes consist of chains of magnetic particles made of either magnetite (Fe₃O₄) or greigite (Fe₃S₄) and are organized in a linear conformation by a protein scaffold within invaginations of the cell membrane. The bacteria align along the north–south magnetic field lines, much like a compass needle. They are typically microaerophilic or anaerobic and are commonly found near the...

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Related Experiment Video

Updated: May 11, 2026

Standardized Data Acquisition for Neuromelanin-Sensitive Magnetic Resonance Imaging of the Substantia Nigra
05:14

Standardized Data Acquisition for Neuromelanin-Sensitive Magnetic Resonance Imaging of the Substantia Nigra

Published on: September 8, 2021

[Paramagnetic calcium melanins].

A V Lebedev, M V Ivanova, A A Timoshin

    Biofizika
    |May 9, 2013
    PubMed
    Summary
    This summary is machine-generated.

    Calcium ions are crucial for forming paramagnetic "calcium melanins" from various polyphenols using potassium superoxide. These novel melanin-like polymers exhibit stable paramagnetic properties and rapid formation, unlike traditional methods.

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    Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
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    Laser Microdissection-Based Protocol for the LC-MS/MS Analysis of the Proteomic Profile of Neuromelanin Granules
    07:35

    Laser Microdissection-Based Protocol for the LC-MS/MS Analysis of the Proteomic Profile of Neuromelanin Granules

    Published on: December 16, 2021

    Related Experiment Videos

    Last Updated: May 11, 2026

    Standardized Data Acquisition for Neuromelanin-Sensitive Magnetic Resonance Imaging of the Substantia Nigra
    05:14

    Standardized Data Acquisition for Neuromelanin-Sensitive Magnetic Resonance Imaging of the Substantia Nigra

    Published on: September 8, 2021

    Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model
    12:37

    Pharmacologic Induction of Epidermal Melanin and Protection Against Sunburn in a Humanized Mouse Model

    Published on: September 7, 2013

    Laser Microdissection-Based Protocol for the LC-MS/MS Analysis of the Proteomic Profile of Neuromelanin Granules
    07:35

    Laser Microdissection-Based Protocol for the LC-MS/MS Analysis of the Proteomic Profile of Neuromelanin Granules

    Published on: December 16, 2021

    Area of Science:

    • Biochemistry
    • Materials Science

    Context:

    • Melanins are complex biopolymers with diverse functions.
    • The formation of melanin-like pigments is typically a slow autoxidation process.
    • Paramagnetic properties of melanins are of interest for various applications.

    Purpose:

    • To investigate the role of calcium ions in the rapid synthesis of melanin-like pigments.
    • To characterize the properties of novel paramagnetic polymers formed in the presence of calcium.

    Summary:

    • Treatment of various polyphenols (catechol, pyrogallol, DOPA, dopamine, norepinephrine, echinochrome) with potassium superoxide (KO2) and calcium chloride (CaCl2) rapidly yields water-insoluble, paramagnetic pigments termed "calcium melanins".
    • These pigments were not formed without Ca2+ and showed EPR spectra similar to known melanins.
    • EDTA treatment dissolved the pigments and eliminated their EPR signal, indicating calcium's essential role.
    • Similar polymers formed during slower o-diphenol autoxidation in Ca(2+)-containing buffer, highlighting calcium's catalytic role.
    • The study proposes M(2+)-stabilized o-semiquinone radicals or bi-radical complexes as paramagnetic centers.

    Impact:

    • Establishes calcium as a key factor in the rapid formation of M(2+)-catecholate paramagnetic polymers.
    • Offers a new, fast method for synthesizing melanin-like materials with stable paramagnetic properties.
    • Suggests potential applications for these novel paramagnetic polymers in fields requiring stable radical species.