Detection Lambda Research Articles

Changes in the relative amount of subunits of methionine adenosyltransferase in human lymphocytes upon stimulation with a polyclonal T cell mitogen.

Activation of resting human peripheral blood T lymphocytes by the lectin phytohemagglutinin results in an increase in methionine adenosyltransferase (MAT) activity, accompanied by an increase in the amount of the alpha/alpha' catalytic subunits of the enzyme. In contrast, the amount of the noncatalytic beta subunit remains constant throughout the course of the response. Using both polyclonal antibodies to the holoenzyme and monoclonal antibodies to the alpha/alpha' subunits, we detected a cross-reactive 68-kDa protein, which we refer to as lambda. This protein is present in high abundance in resting T cells but decreases upon cell stimulation, as both MAT activity and the amount of the catalytic alpha/alpha' subunits increase. The decrease in lambda and increase in alpha/alpha' occurs after interleukin-2 production and before DNA synthesis. lambda virtually disappears when the cells are actively dividing. Several continuous T cell lines (HPB-ALL, MOLT-4, and Jurkat) as well as a freshly isolated T cell leukemia (ALL-2) had no detectable lambda. The Km for L-methionine for enzyme from resting peripheral blood mononuclear cells was 19-23 microM, which is 3-8-fold higher than purified MAT from fresh leukemic cells or enzyme from Jurkat cells, both of which have a Km of 3.5-3.8 microM. Kinetic analysis of enzyme activity from activated peripheral blood mononuclear cells suggested the presence of two forms of enzyme catalyzing the synthesis of AdoMet. After separation of lambda from the alpha and beta subunits by hydrophobic chromatography, it was determined that lambda has MAT activity but that it is significantly less active than the form containing the alpha subunit. It therefore appears that in resting T cells MAT is sequestered as a less active form. We hypothesize that lambda is a precursor to the catalytic subunits of human lymphocyte MAT and propose that the transition from lambda to alpha/alpha' may be important in the response of T cells to mitogenic signals.

Chromosomal location of structural genes encoding murine immunoglobulin lambda light chains. Genetics of murine lambda light chains.

To determine the chromosomal localization of murine lambda light (L) chain structural genes, DNA from a panel of 11 mouse x hamster somatic cell hybrids was scored for the presence of sequences homologous to cloned lambda DNA probe molecules. Six of the hybrids had detectable lambda I and lambda II gene sequences. In all six, the full complement of murine sequences was present, and in its germline configuration. The remaining hybrids lacked any detectable murine lambda L chain gene sequences. The only mouse chromosome present in all of the positive hybrids and absent from the negative ones was number 16, allowing the assignment of lambda L chain structural genes to this chromosome. Together with the previous assignments of the kappa L chain genes to chromosome 6 and heavy chain genes to chromosome 12, this finding completes the mapping of Ig structural genes in the mouse at the chromosomal level.

Liquid chromatographic identification of oils by separation of the methanol extractable fraction

A liquid chromatographic oil spill identification technique employing dual ultraviolet detection was developed. The methanol-extractable fraction was removed from the oil samples and separated on a reverse-phase column using a water/methanol gradient. Ratios of the peak heights of two closely eluting bands (..cap alpha.. = 1.01; detector lambda = 254 nm), common to all oils studied, were reproducible to within +-3.0 percent. This ratio was used for screening improbable oil spill source samples. A series of intra-chromatographic peak-height ratios was then used to define a ''fingerprint'' region (detector lambda = 210 nm). The spill chromatogram was used as a standard to which all suspects were compared for matching purposes. This matching technique showed that, as an oil weathered, the standard error of the standard deviations between any two chromatograms (weathered and unweathered) increased proportionately to exposure time. This permitted the calculation of an estimated time of spillage (+-8 h) based on the linear increase of the standard error with time, for nine of the eleven oils tested.