QUINONE DISTRIBUTION IN HORSE-CHESTNUT CHLOROPLASTS,GLOBULES AND LAMELLAE

The quinone content of whole and sonicated horse-chestnut chloroplasts was studied over a period of 6 months. Whole chloroplasts show a steady increase of plastoquinone A and C concentrations from May to September. By September 1 about 0.5 μmoles PQ A and about 0.3 μmoles PQ C plus D per mg chlorophyll are found in whole chloroplasts. The osmiophilic globule fraction of sonicated chloroplasts contains traces of PQ A but no PQ C in May. By October 5 equal amounts of PQ A and PQ C plus D (0.15 μmoles per mg chlorophyll) are found in horse-chestnut globules. By Oct. 15 the PQ A content increases at least 20-fold, the PQ C content at least 7-fold. The lamellae fraction of sonicated horse-chestnut chloroplasts contains 0.05 μmoles PQ A and 0.03 μmoles PQ C plus PQ D in May. By October 15 about 0.3 μmoles PQ A and 0 1 μmoles PQ C per mg chlorophyll can be found in lamellae. The total amount of plastoquinones accumulated in the globules accounts for up to 20% of the total accumulation in the chloroplast during the season.     

An improved method for embedding brain tissue in albumin-gelatin.

A new modification of the Snodgrass-Dorsey (1963) albumin embedding method is described. Formalin fixed brains of various ages of rhesus monkey (Macaca mulatta) were sunk in 10% phosphate buffered formalin which contained 30% sucrose, and then embedded in a 3% gelatin, 30% egg albumin solution which had been centrifuged to ensure uniformity. The albumin-gelatin was hardened in formaldehyde fumes and blocks cut frozen at 10-40 micron. Sections thus prepared can be handled easily and mounted without damage to the tissue. Modifications of conventional cell and fiber stains produce high quality finished slides in which the stained brain tissue is surrounded by a colorless albumin-gelatin matrix.     

The NADH oxidizing system of the plasma membrane and metabolic signal control

Summary The development of ideas concerning plasma membrane redox reactions in normal and transformed animal cells is described, with emphasis on transferrin and ceruloplasmin. Control by hormones and growth factors, as well as the NAD⁺/NADH ratio in the cell are important in distinguishing the two types of cells.     

Copper-Based Pulsed Dipolar ESR Spectroscopy as a Probe of Protein Conformation Linked to Disease States

We demonstrate the ability of pulsed dipolar electron spin resonance (ESR) spectroscopy (PDS) to report on the conformation of Cu-Zn superoxide dismutase (SOD1) through the sensitive measurement of dipolar interactions between inherent Cu²⁺ ions. Although the extent and the anisotropy of the Cu ESR spectrum provides challenges for PDS, Ku-band (17.3 GHz) double electron-electron resonance and double-quantum coherence variants of PDS coupled with distance reconstruction methods recover Cu-Cu distances in good agreement with crystal structures. Moreover, Cu-PDS measurements expose distinct differences between the conformational properties of wild-type SOD1 and a single-residue variant (I149T) that leads to the disease amyotrophic lateral sclerosis (ALS). The I149T protein displays a broader Cu-Cu distance distribution within the SOD1 dimer compared to wild-type. In a nitroxide (NO)-labeled sample, distance distributions obtained from Cu-Cu, Cu-NO, and NO-NO separations reveal increased structural heterogeneity within the protein and a tendency for mutant dimers to associate. In contrast, perturbations caused by the ALS mutation are completely masked in the crystal structure of I149T. Thus, PDS readily detects alterations in metalloenzyme solution properties not easily deciphered by other methods and in doing so supports the notion that increased range of motion and associations of SOD1 ALS variants contribute to disease progression.     

Defective visions of the Caribbean: Culture shock in Central American

Insufficient regard has been given to the impact of culture and/or return shock on the document produced by expatriates when they are used in ethnohistorical studies. This paper seeks to rectily this lacuna with on analysis of the fate of two expatriate authors in Central American and their seach for peace and justice.