In:
Israel Journal of Chemistry, Wiley, Vol. 21, No. 4 ( 1981-01), p. 291-295
Abstract:
The addition of 1–50 mM MgCl, to “low salt” thylakoid membranes causes a monotonic decrease in the transverse, aqueous proton relaxation rate ( R 2 = 1/ T 2 ) and an increase in the 6‐line ESR spectrum characteristic of free Mn(II) but does not affect the oxygen evolution rate. These results suggest that magnesium ion at low concentrations replaces Mn(II) from a very loosely bound pool which is not involved in oxygen evolution. The decrease of R 2 is probably due mainly to the smaller molar relaxivity of free compared with bound Mn(II). R 2 can be affected by conformational and structural changes involving the Mn(II) as well as by the amount of Mn(II) and the nature of its binding. However, MgCl 2 causes the same decrease in R 2 for trypsin treated thylakoids, which do not undergo the gross structural changes, e.g. grana stacking, that it produces in untreated membranes. R 2 measurements of isolated light harvesting complex preparations indicate the presence of bound Mn in it; neutron activation analysis of these samples shows that they have about one‐third of the functional manganese bound in thylakoid membranes—this may be the tightly bound pool of Mn, but the results are not conclusive.
Type of Medium:
Online Resource
ISSN:
0021-2148
,
1869-5868
DOI:
10.1002/ijch.198100053
Language:
English
Publisher:
Wiley
Publication Date:
1981
detail.hit.zdb_id:
2066481-3
