Photoemission analysis of chemical differences between the membrane and cytoplasm of neuronal cells

Abstract

We demonstrate the possibility of using x-ray photoemission spectroscopy (XPS) to distinguish between the chemical properties of the neuron membrane and of the cytoplasm in brain cells. This was possible by analysing cells de-capped by using a newly developed technique. The XPS spectra clearly show chemical differences between the cell cytoplasm and the membrane, for example between nitrogen in-NH 2 and-NH 3 , which are characteristic of the proteins and membrane phospholipids, respectively. A preliminary (and not conclusive) interpretation of all the observed spectroscopic features is given.

In situphotoelectron spectroscopy study of water adsorption on model biomaterial surfaces

“…The N1s core level is asymmetric with two maxima at binding energies of 400.1 and 401.7 eV under dry conditions ( figure 9). These binding energies agree well with previously reported values for NH 3 + and NH 2 in phospholipids, proteins and amino acids [17,25], suggesting the presence of deprotonated and, to a lesser extent, protonated NH 2 groups in our experiment. With increasing water vapor pressure, the N1s relative intensity of both peaks changed and the binding energy to 401.4 and 404.3 eV, respectively.…”

Chemical characterization of red cells from the black sea urchin Arbacia lixula by X-ray photoelectron spectroscopy

“…The excess in positive charge, probably is offset by carboxylate, phosphate and sulphone/sulphate non protonate functional groups that can be present on the external membrane. 14 This data is also conrmed by the total absence of MgCO 3 and Na 2 CO 3 . No C 1s peaks are observed at 290.1 and 290.3 eV (see Table 1) as assigned to carbonate groups C 1s experimentally acquired respectively on MgCO 3 and Na 2 CO 3 standard powder samples (Fig.…”

“…In fact, the colorless cells are rich in Na + counter-ions, (Fig. 5, panel C and Table 1) 14,21 , with Cl À /Na + ratio of 0.7 that is quite dissimilar to 1.2 reported value for Cl À and Na + content in seawater. 39 Instead, red cells are enriched in Mg 2+ ions (Fig.…”

“…However, unlike sulfur, the differences in phosphate chemical shi are difficult to be attributed at specic phosphorous functional groups when involved in bio-organic compounds. [14][15][16] The importance of sulphate species has been reported in some studies highlighting that variations in the number of sulphate esters are responsible for various changes in biological activities of natural products. These changes can result in opposite (increase or decrease) biological activity or even in reversal effects.…”

“…Therefore, in cells characterization XPS could not study the cell cytoplasm but can represent a powerful method to explore cell surface (the membrane, less than 10 nm thick, and the proteins embedded in it). 14 To date, this analytical technique has been widely used to study bioorganic systems materials as for example microorganisms and their related systems, as biolms, extracellular polymeric substances, and bio-adhesions. 15 More recently, analysis by nano-ESCA (Electron Spectroscopy for Chemical Analysis) of biological samples, such as blood cells (i.e., neutrophil and platelets) immobilized on suitable surfaces, have been reported for chemical and morphological cell studies, showing that these typologies of bio-organic sample can be analyzed in a condition of ultra-high-vacuum (UHV).…”