All articles starting with N
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Nucleocytoviricota
Nucleocytoviricota, formerly NCLDV, is a phylum of large dsDNA eukaryotic viruses in realm Varidnaviria, kingdom Bamfordvirae, including giant viruses with genomes up to 2.5 Mb and virions to 1.5 μm, plus small mriyaviruses.
Nucleoid
Nucleoid: the membrane-free region of bacterial and archaeal cells holding the condensed chromosome with proteins and RNA. Key facts: 80/10/10 DNA/protein/RNA in E. coli, ~1000-fold compaction, six macrodomains, NAPs like HU and H-NS.
Nucleolar and spindle-associated protein 1
NUSAP1 (NuSAP), nucleolar and spindle-associated protein 1, is a 55 kDa microtubule- and chromatin-binding protein regulating mitotic spindle assembly, RanGTP/importin controlled, overexpressed in many cancers as a prognostic biomarker.
Nucleolar complex protein 2
Nucleolar complex protein 2 (NOC2L, novel INHAT repressor) is a 749-aa human nucleolar protein that inhibits p300 histone acetylation, corepresses p53/p21 transcription, and aids rRNA processing; the name also covers yeast Noc2p and a Rab3-effector Noc2.
Nucleolus
Nucleolus: largest membraneless organelle in the eukaryotic nucleus, site of ribosome biogenesis. Forms around rDNA NORs on acrocentric chromosomes via liquid-liquid phase separation; also regulates stress response, aging, and cancer.
Nucleolus and neural progenitor protein
NEPRO (nucleolus and neural progenitor protein, RMP64, C3orf17, NET17) is a conserved eukaryotic nucleolar protein, an RNase MRP subunit required for 40S ribosomal subunit maturation, implicated in anauxetic dysplasia 3 and cancer cell proliferation.
Nucleolus organizer region
Nucleolus organizer region (NOR), also called nucleolar organizing region: chromosomal locus of tandem ribosomal DNA repeats that seeds the nucleolus; in humans on acrocentric chromosomes 13, 14, 15, 21, 22, detected by AgNOR silver staining.
Nucleon
A nucleon is a proton or neutron, the two baryons that make up atomic nuclei, each built from three quarks and treated as two states of one particle.
Nucleophile
A nucleophile is a chemical species that donates an electron pair to bond with an electron-poor electrophile, playing a central role in organic substitution reactions.
Nucleophilic acyl substitution
Nucleophilic acyl substitution is the reaction in which a nucleophile replaces the leaving group on a carbonyl carbon, converting one carboxylic acid derivative into another.
Nucleophilic aromatic substitution
Nucleophilic aromatic substitution (SNAr) is a class of organic reactions in which a nucleophile replaces a leaving group on an aromatic ring, typically requiring electron-withdrawing groups.
Nucleophilic aromatic substitution of hydrogen
Nucleophilic aromatic substitution of hydrogen, abbreviated SNArH, is a reaction in which a nucleophile directly replaces a hydrogen atom on an aromatic ring, usually requiring an oxidant.
Nucleophilic substitution
Nucleophilic substitution is an organic reaction in which a nucleophile replaces a leaving group on a substrate, proceeding mainly by the SN1 and SN2 mechanisms.
Nucleophilic substitution of alcohols
Nucleophilic substitution of alcohols is the family of reactions replacing an alcohol's hydroxyl group with a nucleophile, proceeding by SN1 or SN2 pathways after acid activation.
Nucleophilicity
Nucleophilicity is the kinetic ability of a chemical species, the nucleophile, to donate electron pairs to an electrophilic partner, measured by reaction rate and distinct from basicity.
Nucleoprotein
Nucleoprotein (N, NP): a protein associated with nucleic acid; in virology, the protein coating the genome of most RNA viruses, forming the nucleocapsid, shielding RNA from nucleases and immune sensors, and serving as the template for transcription and replication.
Nucleoside
Nucleoside: a glycoside of a pyrimidine or purine base with ribose or deoxyribose, also called nucleoside analogs in drugs like acyclovir and AZT; nucleoside plus phosphate equals nucleotide, the DNA/RNA building block.
Nucleoside diphosphate kinase
Nucleoside diphosphate kinase (NDPK, NDK, EC 2.7.4.6; NME/NM23/Awd family) is a conserved oligomeric enzyme that balances cellular NTP pools by ping-pong γ-phosphate transfer through a phosphohistidine intermediate, with added roles in metastasis suppression, histidine phosphorylation, and bacterial virulence.
Nucleoside kinase
Nucleoside kinase, or deoxyribonucleoside kinase (dNK), is a salvage-pathway enzyme phosphorylating deoxynucleosides to monophosphates. Humans have four: TK1, TK2, dCK, dGK; they activate antiviral and anticancer nucleoside analogs.
Nucleoside phosphoramidites
Nucleoside phosphoramidites are protected nucleoside monomers with DMT, base-acyl, and 2-cyanoethyl phosphoramidite groups, introduced in 1981 and used as the standard building blocks for automated DNA and RNA oligonucleotide synthesis.
Nucleoside transporter
Nucleoside transporters (CNTs/SLC28, ENTs/SLC29) move nucleosides and analog drugs across membranes; CNTs are sodium-coupled concentrative symporters, ENTs sodium-independent equilibrative uniporters, key to gemcitabine, ribavirin, and cladribine pharmacology.
Nucleoside triphosphate
A nucleoside triphosphate (NTP) is a molecule of a nitrogenous base, a sugar, and three phosphate groups that serves as the substrate for RNA and DNA synthesis.
Nucleoside triphosphate/diphosphate phosphatase
Nucleoside triphosphate/diphosphate phosphatase, an enzyme activity (NTPDase EC 3.6.1.5; bacterial Ntdp/Sa1684) hydrolyzing NTPs and NDPs to NMPs plus phosphate, Ca/Mg or Mn dependent, central to purinergic signaling and bacterial virulence.
Nucleoside-modified mRNA
Nucleoside-modified mRNA is synthetic messenger RNA in which natural bases are replaced with analogs such as pseudouridine, established by Karikó and Weissman in 2005 and recognized with the 2023 Nobel Prize.
Nucleosome
Nucleosome: basic repeating subunit of chromatin, DNA wrapped around a histone octamer (H2A, H2B, H3, H4) with 146-147 bp, plus linker histone H1; packages and regulates eukaryotic DNA.
Nucleosome assembly
Nucleosome assembly deposits H3-H4 tetramers and H2A-H2B dimers onto DNA via histone chaperones: CAF-1 with PCNA in replication-coupled assembly of H3.1, and HIRA or DAXX in replication-independent assembly of H3.3, with ASF1 as the central handoff chaperone.
Nucleosome assembly protein
Nucleosome assembly proteins (NAPs, e.g. NAP1/Nap1) are conserved histone chaperones with a NAP domain that shuttle H2A-H2B histones, assemble and disassemble nucleosomes, and support replication, transcription, and development across eukaryotes.
Nucleosome-remodeling factor subunit BPTF
BPTF (bromodomain and PHD domain transcription factor), largest subunit of the NURF chromatin-remodeling complex; its PHD finger reads H3K4me3, its bromodomain acetyl-lysines, targeting NURF in development and cancer.
Nucleosynthesis
Nucleosynthesis, also called nucleogenesis, is the set of nuclear processes that create atomic nuclei, from big bang hydrogen and helium to elements forged in stars.
Nucleotide
A nucleotide is the basic building block of DNA and RNA, made of a sugar, a phosphate group, and a base, whose order encodes genetic information.