亲水改性PBS基共聚物的N435酶降解差异性及分子模拟

doi:10.7503/cjcu20140966

摘要/Abstract

摘要：

在水相体系中, 采用脂肪酶Novozym435对聚丁二酸丁二醇酯(PBS)分子主链中氧醚键在醇段和酸段的不同位置的共聚物聚(丁二酸丁二醇-co-丁二酸二甘醇酯)[P(BS-co-BDGA)]和聚(丁二酸丁二醇-co-二甘醇酸丁二醇酯)[P(BS-co-DEGS)]进行酶促降解研究. 以分子对接模拟探讨了酶对亲水性底物的识别及相互作用机制. 通过对降解前后不同摩尔比的共聚物薄膜的质量损失率、亲水性、热性能以及降解产物的分析, 研究了PBS改性共聚物的降解规律. 结果表明, 随着降解时间的推移, 所有共聚物薄膜的质量损失率升高, 亲水性增强, 热分解温度升高; 降解5 d后, P(BS-co-BDGA)降解产生的低聚物种类比P(BS-co-DEGS)的多. 分子对接结果表明, 醚键在酸段的P(BS-co-BDGA)型酯键与Novozym435酶活性位点的结合比醚键在醇段的P(BS-co-DEGS)型酯键更稳定, 因此, 在N435脂肪酶作用下, P(BS-co-BDGA)比P(BS-co-DEGS)的降解效果好. 实验结果表明, 当DGA摩尔分数为20%时, 降解效果最佳.

关键词: 聚丁二酸丁二醇酯, 氧醚键, 脂肪酶N435, 酶促降解, 分子对接模拟

Abstract:

By lipase Novozym435, enzymatic degradation of copolymers poly(butylene succinate-diglycolic butanediol)ester[P(BS-co-BDGA)] and poly(butylene succinate-diethylene glycol succinate)ester[P(BS-co-DEGS)] which contain ether oxygen bond at different positions of alcohol binding segment and acid binding segment in the main chain of PBS, was performed in the aqueous system. And molecular docking simulations explore the recognition of enzyme on hydrophilic substrate and the interaction mechanisms. In order to study the degradation law of PBS modified copolymers, the mass loss rate, hydrophilicity and thermal properties of the copolymer films and the degradation products were investigated. The results show that: with the passage of time, mass loss rate of the copolymer films is increased, increasing the hydrophilicity and the thermal decomposition temperature; after degradation for 5 d, oligomeric species of P(BS-co-BDGA) are more than P(BS-co-DEGS). Combined with the results of molecular docking, P(BS-co-BDGA) ester bond of ether bond in an acid binding segment docking with the Novozym435 enzyme active sites is more stable than P(BS-co-DEGS) ester bond of ether bond in an alcohol binding segment, so under the action of the enzyme. The degradation effect of P(BS-co-BDGA) is better than P(BS-co-DEGS); and in the synthesized composition range, when the addition amount of DGA is 20%(molar fraction), degradation effect is best.

Key words: Polybutylene succinate, Oxygen ether bond, Lipase Novozym 435, Enzymatic degradation, Molecular docking simulation

中图分类号:

O631

TrendMD:

张敏, 张祎, 李成涛, 覃家祥, 高让, 马晓宁, 邱建辉. 亲水改性PBS基共聚物的N435酶降解差异性及分子模拟. 高等学校化学学报, 2015, 36(3): 568.

ZHANG Min, ZHANG Yi, LI Chengtao, QIN Jiaxiang, Gao Rang, MA Xiaoning, QIU Jianhui. N435 Enzymatic Degradation Difference and Molecular Modeling of Hydrophilic Modified PBS-based Copolymer^†. Chem. J. Chinese Universities, 2015, 36(3): 568.

图/表 12

Table 1 Composition and relactive parameters of copolymers

Run	Copolymer	10^-4 M_n	10^-4 M_w	M_w/M_n	Run	Copolymer	10^-4 M_n	10^-4 M_w	M_w/M_n
1	PBS	5.08	10.98	2.16	6	P(BS-co-5%BDGA)	5.48	10.55	2.07
2	P(BS-co-5%DEGS)	4.40	8.17	1.86	7	P(BS-co-10%BDGA)	5.40	13.36	2.48
3	P(BS-co-10%DEGS)	5.20	9.99	1.92	8	P(BS-co-15%BDGA)	4.73	12.54	2.23
4	P(BS-co-15%DEGS)	4.50	9.04	2.01	9	P(BS-co-20%BDGA)	4.91	11.37	2.96
5	P(BS-co-20%DEGS)	4.52	9.13	2.02

Fig.1 1H NMR spectra of copolymers P(BS-co-DEGS)(A) and P(BS-co-BDGA)(B)

Fig.2 Schematic representation of BSB, DEGSDEG and BDGAB

Fig.3 Mass loss of copolymers P(BS-co-DEGS)(---) and P(BS-co-BDGA)(—) during degradation

Table 2 Contact angle of the copolymer

Copolymer	Water contact angle, θ/(°)		Copolymer	Water contact angle, θ/(°)
Copolymer	Before degradation		After degradation of 2 d	Before degradation	After degradation of 2 d
PBS	72.76	67.03	P(BS-co-5%BDGA)	71.46	62.09
P(BS-co-5%DEGS)	68.30	54.12	P(BS-co-10%BDGA)	70.26	51.11
P(BS-co-10%DEGS)	66.18	49.63	P(BS-co-15%BDGA)	65.62	45.03
P(BS-co-15%DEGS)	66.07	42.42	P(BS-co-20%BDGA)	62.57	37.93
P(BS-co-20%DEGS)	64.78	40.65

Fig.4 Curves of decomposition temperature before and after degradation of copolymers P(BS-co-DEGS)(A) and P(BS-co-BDGA)(B)

Table 3 TGA data of copolymers

Copolymer	Before degradation		After degradation of 3 d		Copolymer	Before degradation		After degradation of 3 d
Copolymer	T_d,5%/℃	T_d,50%/℃		T_d,5%/℃	T_d,50%/℃	T_d,5%/℃	T_d,50%/℃	T_d,5%/℃	T_d,50%/℃
PBS	354.54	408.84	361.65	413.62	P(BS-co-5%BDGA)	355.34	392.57	360.12	401.55
P(BS-co-5%DEGS)	360.92	406.72	368.53	413.07	P(BS-co-10%BDGA)	342.78	395.68	355.50	407.62
P(BS-co-10%DEGS)	361.71	409.49	365.28	409.99	P(BS-co-15%BDGA)	352.76	399.53	357.70	406.06
P(BS-co-15%DEGS)	366.15	409.23	366.36	410.60	P(BS-co-20%BDGA)	352.91	404.20	358.31	406.85
P(BS-co-20%DEGS)	360.50	407.91	361.74	408.56

Fig.5 MALDI-TOF-MS spectra of the degradation products of copolymers P(BS-co-15DEGS)(A) and P(BS-co-15BDGA)(B)

Table 4 m/z of the degradation products of copolyester†

Copolymer	[M+Na⁺], m/z	Product
P(BS-co-DEGS)	485.5	L*S(BS)₂·Na⁺
	501.5	L*S(BS)(DEGS)·Na⁺
	517.5	L*S(DEGS)₂·Na⁺
	657.7	L*S(BS)₃·Na⁺
	673.7	L*S(BS)₂(DEGS)·Na⁺
	689.7	L*S(BS)(DEGS)₂·Na⁺
	711.8	C*(BS)₄·Na⁺
P(BS-co-BDGA)	485.5	L*S(BS)₂·Na⁺
	501.5	LS(BS)(BDGA)·Na⁺; L(BS)₂(DGA)·Na⁺
	517.5	LS(BDGA)₂·Na⁺; L(BS)(BDGA)(DGA)·Na⁺
	533.5	L*(BDGA)₂(DGA)·Na⁺
	587.6	C*(BDGA)₃·Na⁺
	605.6	L*(BDGA)₃·Na⁺
	657.7	L*S(BS)₃·Na⁺
	673.7	LS(BS)₂(BDGA)·Na⁺; L(BS)₃(DGA)·Na⁺
	689.7	LS(BS)(BDGA)₂·Na⁺; L(BS)₂(BDGA)(DGA)·Na⁺
	711.8	C*(BS)₄·Na⁺

Table 5 Docking results of substrate molecules using the AutoDock program

Enzyme	Ligand	$E binding a$ / (kJ·mol^-1)	$E inter - mol b$ / (kJ·mol^-1)	$E vdw c$ / (kJ·mol^-1)	$E elec d$ / (kJ·mol^-1)	$E total e$ / (kJ·mol^-1)	$E torsional f$ / (kJ·mol^-1)
N435 lipase	BSB	-15.73	-34.43	-33.60	-0.84	-5.15	19.96
	DEGSDEG	-17.07	-37.03	-36.40	-0.63	-5.19	19.96
	BDGAB	-21.13	-41.09	-40.25	-0.84	-4.52	19.96

Table 5 Docking results of substrate molecules using the AutoDock program

Enzyme	Ligand	$E binding a$ / (kJ·mol^-1)	$E inter - mol b$ / (kJ·mol^-1)	$E vdw c$ / (kJ·mol^-1)	$E elec d$ / (kJ·mol^-1)	$E total e$ / (kJ·mol^-1)	$E torsional f$ / (kJ·mol^-1)
N435 lipase	BSB	-15.73	-34.43	-33.60	-0.84	-5.15	19.96
	DEGSDEG	-17.07	-37.03	-36.40	-0.63	-5.19	19.96
	BDGAB	-21.13	-41.09	-40.25	-0.84	-4.52	19.96

Fig.6 Substrate-enzyme interactions by docking studies for CALB-DEG(A) and CALB-DGA(B)

Fig.7 Substrate-enzyme interactions by docking studies for CALB-DEG(A) and CALB-DGA(B)

参考文献 21

[1]	Matteo G., Andrea N., Michelina S., Giulio Z., Nadia L., Fabio F., Andrea M., Polymer Degradation and Stability,2013, 98, 934—942
[2]	Wang H. J., Li J. X., Wang X. C., Polymer Materials Science and Engineering,2014, 30(6), 73—76
	(王海军, 李金祥, 王学川. 高分子材料科学与工程, 2014, 30(6), 73—76)
[3]	Cui X. H., Wang T. T., Yao J. B., Cong H. L., New Chemical Materials,2014, 42(7), 3—5
	(崔西华, 王婷婷, 姚甲彬, 丛海林. 化工新型材料, 2014, 42(7), 3—5)
[4]	Zhang M., Jing J. J., Li C. T., Wang H., Ma X. Y., Chem. J. Chinese Universities,2014, 35(12), 2706—2712
	(张敏, 荆晶晶, 李成涛, 王慧, 马晓燕. 高等学校化学学报, 2014, 35(12), 2706—2712)
[5]	Liu Y. J., Xie W., Liu Y. W., Fan S. H., Liu P., Polymer Materials Science and Engineering,2013, 29(2), 173—177
	(刘跃军, 谢伟, 刘亦武, 范淑红, 刘磅. 高分子材料科学与工程, 2013, 29(2), 173—177)
[6]	Liu D., Qi Z. G., Xu J., Guo B. H., Plastic,2014, 43(4), 25—29
	(刘丹, 齐治国, 徐军, 郭宝华. 塑料, 2014, 43(4), 25—29)
[7]	Cho K., Lee J., Kwon K., Journal of Applied Polymer Science,2001, 79(6), 1025—1033
[8]	Tokiwa Y., Calabia B. P., Journal of Polymers and the Environment,2007, 15(4), 259—267
[9]	Sivalingam G., Chattopadhyay S., Madras G., Polymer Degradation and Stability,2003, 79, 413—418
[10]	Park H. J., Joo J. C., Park K., Kim Y. H., Yoo Y. J., Journal of Biotechnology,2013, 163, 346—352
[11]	Ni Z., Lin X. F., Journal of Molecular Modeling,2013, 19(1), 349—358
[12]	Liu B., Lian Y. H., Li Z., Chen G. J., Acta Chimica Sinica,2014, 72, 942—948
	(刘蓓, 廉源会, 李智, 陈光进. 化学学报, 2014, 72, 942—948)
[13]	Krieger E., Koraimann G., Vriend G., Proteins,2002, 47(3), 393—402
[14]	Krieger E., Darden T., Nabuurs S., Finkelstein A., Proteins,2004, 57(4), 678—683
[15]	Zhao N., Lü Y. Z., Li G. J., Chem. Res. Chinese Universities,2013, 29(6), 1180—1184
[16]	Duan Y., Wu C., Chowdhury S., Lee M. C., Xiong G. M., Zhang W., Yang R., Cieplak P., Luo R., Lee T., Caldwell J., Wang J. M., Kollman P., Journal of Computational Chemistry,2003, 24(16), 1999—2012
[17]	Uppenberg J., Oehrner N., Norin M., Hult K., Kleywegt G. J., Patkar S., Waagen V., Anthonsen T., Jones T. A., Biochemistry,1995, 34(51), 16838—16851
[18]	Berendsen H. J. C., Postma J. P. M., van Gunsteren W. F., DiNola A., Haak J. R., Journal of Chemical Physics,1984, 81(8), 3684—3690
[19]	Morris G.M., Goodsell D. S., Halliday R. S., Huey R., Hart W. E., Belew R. K., Olson A. J., Autodock, version 4.0.1, The Scripps Research Institute, La Jolla, 2007
[20]	Wallace A. C., Laskowski R. A., Thornton J. M., Protein Engineering Design & Selection,1995, 8, 127—134
[21]	DeLano W. L., PyMOL Molecular Graphics System, Revision 0.99, DeLano Scientific., San Carlos, 2002