envelope

(noun)

an enclosing structure or cover, such as a membrane

Related Terms

Examples of envelope in the following topics:

  • Viral Morphology

    • Enveloped viruses have membranes surrounding capsids.
    • Animal viruses, such as HIV, are frequently enveloped.
    • Enveloped virions like HIV consist of nucleic acid and capsid proteins surrounded by a phospholipid bilayer envelope and its associated proteins.
    • Other envelope proteins include the matrix proteins that stabilize the envelope and often play a role in the assembly of progeny virions.
    • Because of the fragility of the envelope, non-enveloped viruses are more resistant to changes in temperature, pH, and some disinfectants than are enveloped viruses.

  • Attachment and Entry of Herpes Simplex

    • Herpes simplex virus attaches to a host's cells with viral envelope glycoproteins, which then allows entry of the viral capsid into the host cell.
    • Finally, a stable entry pore is formed through which the viral envelope contents are introduced to the host cell .
    • Initial interactions occur when viral envelope glycoprotein C (gC) binds to a cell surface particle called heparan sulfate.
    • These interactions bring the membrane surfaces into mutual proximity and allow for other glycoproteins embedded in the viral envelope to interact with other cell surface molecules.
    • Following attachment, the viral envelope fuses with the host cell membrane and the viral capsid gains entry into the cell.

  • Virus Classification

    • Viruses are classified by factors such as their core content, capsid structure, presence of outer envelope, and how mRNA is produced.
    • Enveloped viruses have membranes surrounding capsids.
    • Animal viruses, such as HIV, are frequently enveloped.
    • Capsids are classified as naked icosahedral, enveloped icosahedral, enveloped helical, naked helical, and complex .
    • Viruses can also be classified by the design of their capsids which are classified as naked icosahedral, enveloped icosahedral, enveloped helical, naked helical, and complex.

  • Replication of Herpes Simplex Virus

    • HSV-1 undergoes a process of primary and secondary envelopment.
    • The primary envelope is acquired by budding into the inner nuclear membrane of the cell.
    • The virus acquires its final envelope by budding into cytoplasmic vesicles.
    • Entry of HSV into the host cell involves interactions of several glycoproteins on the surface of the enveloped virus, with receptors on the surface of the host cell.
    • The envelope covering the virus particle, when bound to specific receptors on the cell surface, will fuse with the host cell membrane and create an opening, or pore, through which the virus enters the host cell.

  • Animal Viruses

    • Non-enveloped or "naked" animal viruses may enter cells in two different ways.
    • Enveloped viruses also have two ways of entering cells after binding to their receptors: receptor-mediated endocytosis and fusion.
    • Many enveloped viruses enter the cell by receptor-mediated endocytosis in a fashion similar to some non-enveloped viruses.
    • On the other hand, fusion only occurs with enveloped virions.
    • These viruses, which include HIV among others, use special fusion proteins in their envelopes to cause the envelope to fuse with the plasma membrane of the cell, thus releasing the genome and capsid of the virus into the cell cytoplasm.

  • Suggestions for reducing paper use

    • Reuse paper, envelopes, and boxes whenever possible.
    • The Washington Suburban Sanitary Commission decided to replace its billing envelopes with send-and-return envelopes that could be used for both billing and receiving payments.
    • As a result, 47 m3 of warehouse space immediately became available and the cost of envelope purchases was reduced by $55,000.

  • Viral Exit

    • Enveloped viruses (e.g., HIV) typically are released from the host cell by budding.
    • During this process the virus acquires its envelope, which is a modified piece of the host's plasma or other, internal membrane.
    • However, they require an envelope to enclose the DNA as well as to bind with the other healthy cells so that they can infect.
    • "Budding" through the cell envelope, in effect using the cell's membrane for the virus itself is most effective for viruses that need an envelope in the first place .
    • These include enveloped viruses such as HSV, SARS, or smallpox.

  • Gram-Positive Cell Envelope

    • Gram-positive bacteria have cell envelopes made of a thick layer of peptidoglycans.
    • They lack the outer membrane envelope found in Gram-negative bacteria.

  • General Morphology

    • Envelope - Some species of virus envelop themselves in a modified form of one of the cell membranes, either the outer membrane surrounding an infected host cell or internal membranes such as nuclear membrane or endoplasmic reticulum, thus gaining an outer lipid bilayer known as a viral envelope.
    • Viruses can have a lipid "envelope" derived from the host cell membrane.

  • HIV Attachment and Host Cell Entry

    • HIV enters macrophages and CD4-positive T cells (CD4 is a glycoprotein receptor found on cells) by the adsorption of glycoproteins on its surface to receptors on the target cell, followed by fusion of the viral envelope with the cell membrane and the release of the HIV capsid into the cell .
    • Entry to the cell begins through interaction of the trimeric envelope complex and both CD4 and a chemokine receptor on the host cell on the cell surface.
    • Once gp120 is bound with the CD4 protein, the envelope complex undergoes a structural change, exposing the chemokine binding domains of gp120 and allowing them to interact with the target chemokine receptor.