Nucleoplasm



Editor-In-Chief: Henry A. Hoff

=Overview=

Similar to the cytoplasm of a cell, the nucleus contains nucleoplasm or nuclear sap. The nucleoplasm is one of the types of protoplasm, and it is often enveloped by the nuclear membrane or nuclear envelope. The nucleoplasm is a highly viscous liquid that surrounds the chromosomes and nucleoli. Many substances such as nucleotides (necessary for purposes such as the replication of DNA) and enzymes (which direct activities that take place in the nucleus) are dissolved in the nucleoplasm. The nucleoplasm is not a disorganized mass of jelly but a highly structured cell compartment formed of a nucleoskeleton. For example, a network of fibers known as the nuclear matrix can be found in the nucleoplasm. The nucleoplasm is partly made up of nucleohyaloplasm and nucleosol. The nucleoplasm is also colorless.

=Introduction=

A plasm is a formative or formed material; i.e., something molded. Usually a formed material keeps it shape once the mold is removed. Should something be glassy or transparent it can be said to be hyaloid. Whether a fluid is molded or liquid is often a matter of viscosity and whether a fluid is transparent, translucent, or opaque is often a matter of absorption or scattering.

=Visibility of the nucleoplasm=

Factors that can increase the visibility of the nucleoplasm include the state of lateral aggregation of deoxyribonucleic acid and the presence of fibrils. In E. coli, for example, the nucleoplasm has a formed shape that can be altered by fixation.

=Nuclear localization=

The subcellular distribution of a substance to or within the nucleus is often referred to as nuclear localization.

Nucleophosmin has been found to require ATP and/or CTP for translocation (taking approximately 2-4 hrs) from nucleoli into the nucleoplasm as verified by immunofluorescent localization. The redistribution of nucleophosmin into the nucleoplasm was considered uniform, occurs during interphase or differentiation, and is a normal cellular process.

=Binding to the nucleoplasm=

As a molded material, the nucleoplasm can serve as a target for binding molecules. For example, thyroid hormones have been found to bind to it.

=Macromolecular crowding=

The nucleoplasm contains large amounts of macromolecules, which can alter how molecules behave, through macromolecular crowding. Since some of these macromolecules have less volume to move in, their effective concentration is increased. This crowding effect can produce large changes in both the rates and chemical equilibrium for reactions in the nucleoplasm. It is particularly important in its ability to alter dissociation constants by favoring the association of macromolecules, such as when multiple proteins come together to form protein complexes, or when DNA-binding proteins bind to their targets in the genome.

Macromolecular crowding provides the nucleoplasm with strongly viscoeleastic properties and renders the diffusion of soluble proteins anomalous. The cytoplasm is somewhat more crowded than the nucleoplasm.

Using computer simulation, it has been shown that crowding significantly enhances the rate and extent of macromolecular associations of proteins and larger structures for small radii relative to normal diffusion, but for larger radii the probability of finding the target massively decreases below that of normal diffusion, which itself decreases quite rapidly and becomes <1% when starting at a distance that exceeds the target's 10-fold radius.

=References=

Кариоплазма Karyoplazma Karyoplasma Nucleoplasma Nucléoplasme Nucleoplasma Nukleoplazma Nucleoplasma Нуклеоплазма