Cell Bio 11.11.09 -DNA anti parallel double helix 3´and 5´ end between the strands hydrogen bonds major groove and minor groove spherical hindrance makes other parings impossible circular molecule in bacteria chloroplasts mitochondria several viruses problems when denatured or during replication · tension in the rest · when opened at the middle extra twist tighter bindings to the bindings right and left · super-coiling (telephone) · structure → super-coil simian virus 40 → double stranded DNA virus, infects monkeys · picture shows super-coiling · we must get able to get rid of the super-coiling → special type of enzymes · topoisomorases · either bind one or two strands and “entwirre­n” the DNA DNA extraction · 1. DNA is in the nucleus of the cell · 2. cell membrane is disrupted with a detergent interfere with the lipid structure · 3.alcohol is added to separate DNA from other cell components DNA migrates in the electric field → gel-electrophor­esi­s · sort nucleotides by seize · restrictionendo­nuc­lease producing of predictable pieces of DNA DNA is able to denature and renature melting temperature, d
Cloning: Definition, types and stemm cell research Table of contents: Definiton of clones 3 types of cloning Stem cell research , Definition of Stem cells, iPS cells Vocab What are clones? -Clones are defined by having identical genetic material. That means their sequence of bases in their DNA is exactly the same. A DNA consists out of 4 bases. Twins are an example for being clones, because they do have exactly the same DNA. Another example is a Bacterium. It can clone/ replicate himself and is used in science. The 3 types of cloning: It is especially used for one of the 3 types of cloning – the Recombinant DNA Technology ENTER -To make use of this technique, scientists take a DNA fragment containing the gene, they want to clone. -Then they connect the gene with a cloning vector (transport medium) in the lab. -They both form a recombinant DNA molecule. -Now you introduce it into suitable host cells, in this case a bacterium. As we already heard a bacterium can replicate himself and the gene you want to clone is replicated with. ~The next topic is the Reproductive Cloning, as you already can see in the background Dolly the sheep is cloned by this technique Dolly the sheep: Dolly was the first mammal to be cloned. A group of scientist at the Roslin Institute in Scotland cloned the sheep, which was born on 5th July in 1996. Reproductive Cloning: So how did they manage it to clone Dolly? -The Reproductive Cloning process begins
T cell ion channels and their role for activation
T-Zell Aktivierung und die Rolle von Ionenkanälen
T cell ion channels and their role for T cell activation
1.) T cells
As well as B-cells and natural killer cells (NK), T cells belong to the lymphocytes and present a hallmark of the adaptive immunity in vertebrates.
All T cells originate from a progenitor cell in the bone narrow and undergo maturation in the thymus. During maturation the T lymphocytes are being provided with different membrane-bound receptors and cell surface markers distinguishing distinct T cell subsets with unique functions.
T cell subsets: Depending on the composition of their T cell antigen receptor (TCR) the T cells are subdivided into αβ-T cells and γδ-T cells. Αβ-T cells account for the biggest part of the T cells with around 90-95% and represent about 70% of all peripheral blood mononuclear cells (PBMC).
They circulate continuously from the bloodstream to the lymphatic system and lymphoid organs back to the blood, making contact with antigen presenting cells (APCs). The most important factor for the recognition of different antigens is the T cell receptor (TCR). The α- and β-chains of the heterodimeric TCR are composed of a variable and a constant region, which during maturation are spliced together into a single type of functional αβ-TCR which differs in every T cell.
A further determination of αβ-T cells is made by the expression of different co-receptors on the plasma membrane during thymic maturation.
T cells express either a CD4 co-receptor (CD4+) or a CD8 co-receptor (CD8+) involved in TCR signaling .....[read full text]
T cell activation: Although specific activation and signaling of T cells also depend on their subset, the main principles of the stimulation process and signaling pathways are common in most T cells.As mentioned aboveT cell activation requires TCR and co-stimulatory receptor engagement, both of which can be supplied by an activated APC.
Crucial for the transduction of the signal after TCR-binding is the CD3 cluster, a hexameric complex closely associated with the TCR presenting a total of 10 immunoreceptor tyrosine-based activation motifs (ITAMs) (Guy & Vignali 2009). Additionally, non-covalent linked CD8 or CD4 co-receptors bind to the non-polymorphic regions of the same agonist MHCI or MHCII .....
Thirdly, DAG is also able to activate Ras, which continues the signal through phosphorylation events finally initiating the formation of the master transcription factor activator protein 1 (AP-1) (reviewed in Genot & Cantrell 2000). The activation of these transcription factors does not only induce transcription of specific effector molecules specific for each cell but also induces IL-2 production promoting T cell growth (Jain 1995).
2.) T cells and ion channels
For a long time now, it is appreciated that the influx of Ca2+ plays an essential role for triggering T cell activation after TCR engagement.
Remarkably, about 75% of all activation-regulated genes are dependent on Ca2+ influx through the plasma membrane (also see chapter signaling pathways.....
Interestingly, both potassium channels can be specifically blocked by toxins or small organic compounds (Kalman 1998; Srivastava et al. 2008; Srivastava et al. 2005) and show different expression patterns on different T cell subtypes, increasing from resting or naïve to active subtypes (Cahalan et al. 2001). Since blockade of potassium channels, especially Kv1.3, results in suppression of proliferation and effector functions they have been proven as attractive targets for selective immunosuppression in autoimmune disorders.
For example, since T cells are involved in acute rejection of transplanted organs and acute graft-versus-host disease, the blocking of Kv1.3 and KCa3.1 channels could enhance treatment of these clinical implications .....