Buffer P2

Buffer P2 is a lysis buffer solution produced by Qiagen. It contains sodium dodecyl sulfate (SDS) to puncture holes in cellular membranes. It is used in conjunction with other resuspension buffers and lysis buffers to release DNA from cells, often as part of the alkaline lysis method of purifying plasmid DNA from bacterial cell culture.

Buffer

Buffer may refer to:

Separating or cushioning

Physical science

Technology

Buffer (rail transport)

A buffer is a part of the buffers-and-chain coupling system used on the railway systems of many countries, among them most of those in Europe, for attaching railway vehicles to one another.

Fitted at the ends of the vehicle frames, one at each corner, the buffers are projecting, shock-absorbing pads which, when vehicles are coupled, are brought into contact with those on the next vehicle. The draw chain used between each pair of vehicles includes a screw which is tightened after coupling to shorten the chain and keep the buffers pressed together. Such is known as a 'screw coupling'. Historically, coupling chains were no more than that, a short length of heavy chain (typically three links long) with no adjustment. These would result in a 'loose-coupled train' in which the buffers of adjacent vehicles would only touch when the coupling chain was fully slack, such as when being pushed or going down hill.

Although the buffers in the very earliest days of railways were rigid (dumb buffers), they soon came to be spring-loaded, while those fitted to modern locomotives and rolling stock incorporate oleo-pneumatic shock absorbers.

Buffer solution

A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small or moderate amount of strong acid or base is added to it and thus it is used to prevent changes in the pH of a solution. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. Many life forms thrive only in a relatively small pH range so they utilize a buffer solution to maintain a constant pH. In nature, the bicarbonate buffering system is used to regulate the pH of blood.

Principles of buffering

Buffer solutions achieve their resistance to pH change because of the presence of an equilibrium between the acid HA and its conjugate base A⁻.

When some strong acid is added to an equilibrium mixture of the weak acid and its conjugate base, the equilibrium is shifted to the left, in accordance with Le Chatelier's principle. Because of this, the hydrogen ion concentration increases by less than the amount expected for the quantity of strong acid added. Similarly, if strong alkali is added to the mixture the hydrogen ion concentration decreases by less than the amount expected for the quantity of alkali added. The effect is illustrated by the simulated titration of a weak acid with pK_a = 4.7. The relative concentration of undissociated acid is shown in blue and of its conjugate base in red. The pH changes relatively slowly in the buffer region, pH = pK_a ± 1, centered at pH = 4.7 where [HA] = [A⁻]. The hydrogen ion concentration decreases by less than the amount expected because most of the added hydroxide ion is consumed in the reaction