Question

When researches incubate whole red blood cells with lactoperoxidase, hydrogen peroxide and radioactive iodine I 125 and then separate the proteins in SDS gel, several radioactive lines are obtained cause iodine binds to prominent tyrosine and histidine residues outside the cell membrane.
When researches incubate whole red blood cells with galactose oxidase and reduce them with sodium borohydride that contains tritium (H-BH43) several radioactive lines are obtained which are just some of the proteins that have been marked with radioactive iodine , thus galactose residues stand out of the cell.
a) Explain the difference in the number of proteins obtained in the two experiments above
b) Why the results of the second experiment do not reflect mark of all the sugars in the membrane?
c) What results will be obtained if we conduct an experiment identical to that described in the question but with inverse vesicles (these are closed vesicles containing all membrane components but where the outer leaf of the membrane turns inward and inward leaf outward)? Thank you!

Answer 1

ANS a) Iodine-125 has a specific activity of 2170 ci according to matom (80 tbq per matom) and consequently the incorporation of one iodine atom in keeping with peptide or protein molecule will yield material with a particular pastime of 2170 ci in step with mmole. labelling with iodine-125 usually entails incorporation of iodine-125 into tyrosine or histidine residues within the peptide or protein. that is achieved through remedy of the pattern with na125i within the presence of an oxidising reagent to generate a source of electrophilic iodine. usually, one or two iodine atoms are delivered to every tyrosine residue depending on conditions used. the same old oxidant is chloramine-t but milder, more selective reagents at the moment are available such as iodogen or the enzyme lactoperoxidase. for peptides and proteins missing on hand tyrosine residues, unfastened amines can be derivatived with bolton-hunter reagent prior to iodination.both of these strategies result in quite drastic modification of the physical houses of the peptide concerned and although the specific activities of such compounds can be high they do not always own the organic traits of the discern compounds. there may also be a good sized degree of heterogeneity due to the situations of labelling. as legitimate receptor binding research require labelled ligands with bodily properties and biological activities identical to the ones of the unlabelled ligand, labelling with tritium is frequently favored. this leads to a molecule owning surely same residences to the ones of the figure compound, as there has been no gross modification of its primary structure, while affording a cloth of appreciable specific radioactivity.

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ANS b) There can also be a considerable degree of heterogeneity due to the situations of labelling. as valid receptor binding studies require labelled ligands with bodily residences and biological activities same to the ones of the unlabelled ligand, labelling with tritium is regularly desired. this results in a molecule owning sincerely same homes to the ones of the parent compound, as there was no gross change of its primary shape, even as affording a material of appreciable unique radioactivity.

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ANS c) Leaves revel in a combination of demands under frequently destructive conditions. they ought to intercept daylight and facilitate the uptake of co2, which exists at ranges round 390 ppm (µl l-1) in the ecosystem, whilst proscribing water loss. the extensive variety of shapes, sizes and inner structures of leaves suggest that many answers exist to meet those blended needs.In nature, photon irradiance (photon flux density) can range over three orders of value and those modifications can be fast. but, plant life have developed with photosynthetic systems that perform maximum correctly at low mild. such performance confers an apparent selective advantage beneath mild dilemma, but predisposes leaves to photodamage underneath robust light. first, some tolerance is executed via distributing mild over a massive populace of chloroplasts held in architectural arrays inside mesophyll tissues. second, every chloroplast can perform as a apparently impartial entity with respect to photochemistry and biochemistry and might range allocation of assets among photon seize and ability for co2 assimilation in reaction to mild climate. photon absorption is astonishingly speedy (unmarried activities lasting 10–15 s). subsequent energy transduction into nadph and atp is relatively ‘gradual’ (10–4 s), and is accompanied with the aid of co2 fixation through rubisco at a sedate tempo of 3.five occasions consistent with 2nd in line with energetic website. dispensing light absorption between many chloroplasts equalises effort over a massive populace of these organelles, however also reduces diffusion barriers by spreading chloroplasts over a big mesophyll cell floor area inside a given leaf location. the internal structure of leaves (proven inside the follwing segment) displays this want to maximize co2 exchange among intercellular airspace and chloroplasts and to distribute mild extra uniformly with depth than might arise in a homogeneous solution of chlorophyll.