実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF Experimental Report

提出日 Date of Report2017 Feb 27

課題番号 Project No.

装置責任者 Name of responsible person

2017B0138

高田

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）慎一

Quantitative evaluation of uniformity of various polymer networks BL-15 Small and Wide Angle Neutron
by small angle neutron scattering (SANS) with contrast variation

Scattering Instrument (TAIKAN) /BL-15technique

実施日 Date of Experiment

実験責任者名 Name of principal investigator

20/1/2018-23/1/2018

Xiang Li所属 Affiliation
The University of Tokyo
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
PEG/DNA conjugate in D2O/H2O buffer
1. Tetra-functional poly(ethylene glycol)s (Mw = 40,000, conc. = 1 mM )2. 16mer sense- and anti-sense DNA strands
3. Buffer {D2O 63.2%, H2O 36.8 %, sodium phosphate 25 mM, ethylenediaminetetraacetic acid 1 mM,pH 7.4}

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

By reacting Tetra-PEG with DNA, DNA-terminated Tetra-PEG (Tetra-PEG/DNA) were synthesized (Figure 1).
There are two types of Tetra-PEG/DNA. One is sense-DNA/PEG conjugate and another is anti-sense-DNA/PEG
conjugate. By mixing these two types tetraPEG/DNA conjugate at room temp., the gel was formed in the 1mmthick demountable cell due to the physical bond between sense and anti-sense DNA strands.

Figure 1. Schematic of PEG/DNA conjugate and its gel
Because strength of physical bond between DNA depends on temperature, the sol-gel transition occurrs bychanging the temperature. The sol-gel transition point is about 55 ℃ by rheological measurement in lab.

1

2. 実験方法及び結果（つづき） Experimental method and results (continued)
We have measured this Tetra-PEG/DNA gel by using small-angle neutron scattering (SANS) at differenttemperatures from 5-75ºC for cycles to check the structure due to sol-gel transition and the hysteresis.
Every sample was well sealed and place in the 10 positions auto sample changer with temperature control. The
run time for each sample was 1.5 hour and it took about 0.5 hour for the temperature to stabilize at eachtemperature. At the temperature lower than 15ºC, we sealed the sample changer with dried nitrogen gas to prevent
condensation on the sample window. Figure 2 shows the SANS profiles of tetraPEG-sene-DNA/tetraPEG-antisense-DNA mixture and Figure 3 shows the profiles of tetraPEG-sense-DNA. In Figure 2, the scattering peaks
were observed at q ~ 0.03Å-1, which is because of the electrostatic interaction between DNAs as expected. There
was no hysteresis after cycles of heating and cooling, indicating the very site specific and reproducible bonds
between DNAs unlike the other physical gels like gelatin or agarose. In Figure 3, the scattering peak at q ~ 0.03Å1

was also observed and there was no hysteresis. Surprisingly, the SANS profiles of the tetraPEG-sene-DNA/tetraPEG-anti-sense-DNA mixture and tetraPEG-sene-DNA only solution was exactly the same. This might
indicate the homogeneity of this hydrogel, but we still need more low-q data to confirm this. The additional
experiment is scheduled in the Bio-SANS at NIST at the second half of this year. Now, we are trying to get morequantitative analysis with an empirical equation often used for polyelectrolyte solutions:𝐼(𝑞) =𝐵+𝐶
1 + (|𝑞 − 𝑞∗ |𝐿)?

where q* is the peak top position, L is the peak width, m relates to the decreasing slope at high-q side, B and Care system dependent constants. Although the physical meaning of these parameters is still in discussion, it isclear that q* remains constant both in sol and gel state. The correlation length of the peak in real space is around
20 nm, which is much larger than the size of macromonomers (Tetra-PEG/DNA) (Rg ~5 nm from calculation).

5465410-1

654

3

3

2

10Heating
5℃
15℃
25℃
35℃
45℃
55℃
65℃
75℃

2-1

-1

Sol sample

3I(q) / cmI(q) / cm-1

2

1054Sol-gel sample
1st cooling 1st heating 2nd cooling
75℃
35℃
65℃
65℃
45℃
55℃
55℃
55℃
45℃
45℃
65℃
35℃
35℃
75℃
25℃
25℃
15℃
5℃

32-223456 7 8 9-1

10-1q /Å23456 7 8 9

10

100-2
234

5 6 7 8 9-1

10-1q /Å234

5 6 7 8 9100Figure 2. SANS profiles of tetraPEG-sene-DNA/tetraPEG-anti-sense-DNA mixture and tetraPEG-sene-DNA
only solution with repetitive heating and cooling cycles. All the scattering profiles at the same temperature exactlyoverlap each other, indicating no hysteresis in our sample.

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