Photon Factory Activity Report 2019 #37 (2020)

BL-27A/2018G0733

X-ray absorption spectroscopy of condensed sugar-phosphates
Hiromi IKEURA-SEKIGUCHI 1,* and Tetsuhiro SEKIGUCHI 2
Research Institute for Measurement and Analytical Instrumentation (RIMA),
National Metrology Institute of Japan (NMIJ),
National Institute of Advanced Industrial Science and Technology (AIST),
1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, Japan
2
Japan Atomic Energy Agency (JAEA), Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
1

2 Experiment
Experiments were performed at beamline BL-27A withan InSb(111) double-crystal monochromator with anenergy resolution of ca. 0.8 eV around P K-edge. The XAS
spectra of polycrystalline thymidine 5'-monophosphate
calcium salt (TMPCa), thymidine 5'-monophosphate
disodium salt (TMPNa2), and α-tricalcium phosphate(α-Ca3(PO4)2: α-TCP) were measured using monitoring
sample drain current near the P K-edge (2145–2185 eV)and normalized to the incident flux with a thin aluminum
film detector downstream of the sample chamber. Suchenergies were chosen to excite the P 1s core electron to 3p
and 4p unoccupied orbitals. The X-ray energy wascalibrated by reference to the lowest sharp peak oftetraphenylphosphonium bromide (PPh4Br) as 2147.8 eV.
3 Results and Discussion
Fig. 1 shows P K-edge XAS spectra of polycrystalline
TMPCa, TMPNa2, and α-TCP. TMPNa2 has deliquescence
property and absorbed moisture from the atmosphere
during mounting, transforming into gel phase before
entering vacuum chamber. Based on previous study [2],peak A is assigned to P 1s → 3p transition. Peak B and C
are assigned to P 1s → P-O-P chains in condensed
phosphates corresponds to a chemical variation in the 2nd
coordination sphere of P. Features of peak A in TMPCaand TMPNa2 are resemble in each other but the peak
position of TMPNa2 is slightly shifted to higher energy(∼0.2 eV) than that of α-TCP. This shift would be causedby difference in P oxidation states, which depends on thecharge density of counterions and crystalline structures.

The shoulder peak B is slightly observed in both TMPCaand TMPNa2, as broad features. The intensity of peak B inTMPCa is larger than that in TMPNa2. The result is inagreement with the case of inorganic phosphates, where Na
salt shows only small amount of peak B. In general, peak
B and C are characteristic signatures of Ca-P andextensively used as distinct fingerprints for Ca-phosphates
in minerals [3]. The peak C was not observed in TMPNa2
but very slightly in TMPCa. This suggests that structuralconfigurations are more effect to produce the peak C. The
mechanisms of interaction between metal cations andsugar-phosphates will be investigated further.

AP K-edge
α-TCPTMPCaTMPNa2

Intensity (arb. units)1 Introduction
One of the most important acids in biological systems isphosphoric acid (H3PO4) that is usually present in its
ionized form, phosphate (PO43-). Phosphate is a key
element in building blocks of life; forming the nucleicacids DNA and RNA, as phosphodiester backbone [1]. ATP(adenosine triphosphate), an anhydride of phosphoric acidacts as energy storage and transfer within the cell.
Phospholipids consisting of two fatty acid tails and aphosphate group head are the structural basis of all cell
membranes. Despite importance of phosphate compounds
in biological systems, their electronic structures are lessunderstood than those of inorganic phosphates. In order tounderstand electronic structures of condensed sugarphosphates, X-ray absorption spectroscopy (XAS) spectra
were measured near the P K-edge.

BC

2150

2155

2160

2165

Photon Energy(eV)Fig. 1: P K-edge XAS of polycrystalline TMPCa (bluespectrum), TMPNa2 (green spectrum), and α-TCP (redspectrum).
References[1] K. Ruiz-Mirazo, C. Briones, and A. De La Escosura,
Chem. Rev. 114, 285 (2014).
[2] R. Franke, and J. Hormes, Phyica B 216, 85 (1995).
[3] S. Sato, D. Solomon, C. Hyland, Q. M. Ketterings,and J. Lehmann, Environ. Sci. Technol. 39 (19), 7485
(2005).
* ikeura-sekiguchi@aist.go.jp