Heterosynaptic plasticity in biomembrane memristors controlled by pH.
Heterosynaptic plasticity in biomembrane memristors controlled by pH.
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DOI：
10.1557/s43577-022-00344-z
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发表时间：
2023
期刊：
影响因子：
5
通讯作者：
Collier, C. Patrick
中科院分区：
文献类型：
--
作者：
McClintic, William T.;Scott, Haden L.;Moore, Nick;Farahat, Mustafa;Maxwell, Mikayla;Schuman, Catherine D.;Bolmatov, Dima;Barrera, Francisco N.;Katsaras, John;Collier, C. Patrick
在生物学中，异突触可塑性在联合学习和记忆期间维持突触输入的稳态，并引发突触强度的长期变化，从而非特异性地调节不同的突触类型。在生物启发的神经形态电路中，异突触可塑性可以用于扩展两端仿生忆阻器的功能。在这篇文章中，我们探讨了液滴界面双层水溶液的pH值的变化如何调节的pH值范围4.97-7.40的脂质双层膜的忆阻响应。令人惊讶的是，我们没有发现决定性的证据pH值依赖性的电压阈值（V*）的变化所需的丙甲霉素离子通道形成的膜。然而，我们确实观察到一个明确的调制在随时间变化的pH值的孔形成的动力学，脉冲电压实验。此外，在相同的电压下，降低pH导致更高的稳态电流，因为膜中的导电肽离子通道的数量增加。这是由于在pH 4.97下丙甲霉素单体向膜中的分配增加，pH 4.97低于肽的谷氨酸残基上的羧酸酯基团的pKa（约5.3-5.7），使得单体更疏水。在酸性条件下，这些残基上的负电荷的中和增加了膜中肽单体的浓度，使膜中肽聚集体组装体的平衡浓度移动，以有利于更大数量的更大的、越来越导电的孔。它还增加了孔隙形成和衰减的弛豫时间常数，并增强了器件开关特性的短期促进和抑制。调节这些阈值的整体和独立的丙甲霉素浓度和施加的电压将使组装的神经形态计算电路具有增强的功能。我们描述了如何使用pH值作为一个调制的“interneuron”，通过改变双层的结构和动力学性质的脂质双层中的丙甲霉素离子通道的电压依赖性忆阻的变化。具有从电压或离子通道浓度独立地控制孔传导的阈值水平的能力使得能够在神经形态系统中实现额外水平的可编程性。在这篇文章中，我们注意到，通过降低溶液pH值，可以降低膜结合离子通道的传导障碍，从而产生更高的电流，并以成对脉冲促进的形式增强短期学习行为。使用环境变量（如pH值）调整阈值提供了额外的训练和学习算法，可用于在尖峰神经网络中引出复杂的功能。在线版本包含补充材料，可通过10.1557/s43577-022-00344-z获得。
In biology, heterosynaptic plasticity maintains homeostasis in synaptic inputs during associative learning and memory, and initiates long-term changes in synaptic strengths that nonspecifically modulate different synapse types. In bioinspired neuromorphic circuits, heterosynaptic plasticity may be used to extend the functionality of two-terminal, biomimetic memristors. In this article, we explore how changes in the pH of droplet interface bilayer aqueous solutions modulate the memristive responses of a lipid bilayer membrane in the pH range 4.97–7.40. Surprisingly, we did not find conclusive evidence for pH-dependent shifts in the voltage thresholds (V*) needed for alamethicin ion channel formation in the membrane. However, we did observe a clear modulation in the dynamics of pore formation with pH in time-dependent, pulsed voltage experiments. Moreover, at the same voltage, lowering the pH resulted in higher steady-state currents because of increased numbers of conductive peptide ion channels in the membrane. This was due to increased partitioning of alamethicin monomers into the membrane at pH 4.97, which is below the pKa (~5.3–5.7) of carboxylate groups on the glutamate residues of the peptide, making the monomers more hydrophobic. Neutralization of the negative charges on these residues, under acidic conditions, increased the concentration of peptide monomers in the membrane, shifting the equilibrium concentrations of peptide aggregate assemblies in the membrane to favor greater numbers of larger, increasingly more conductive pores. It also increased the relaxation time constants for pore formation and decay, and enhanced short-term facilitation and depression of the switching characteristics of the device. Modulating these thresholds globally and independently of alamethicin concentration and applied voltage will enable the assembly of neuromorphic computational circuitry with enhanced functionality. We describe how to use pH as a modulatory “interneuron” that changes the voltage-dependent memristance of alamethicin ion channels in lipid bilayers by changing the structure and dynamical properties of the bilayer. Having the ability to independently control the threshold levels for pore conduction from voltage or ion channel concentration enables additional levels of programmability in a neuromorphic system. In this article, we note that barriers to conduction from membrane-bound ion channels can be lowered by reducing solution pH, resulting in higher currents, and enhanced short-term learning behavior in the form of paired-pulse facilitation. Tuning threshold values with environmental variables, such as pH, provide additional training and learning algorithms that can be used to elicit complex functionality within spiking neural networks. The online version contains supplementary material available at 10.1557/s43577-022-00344-z.
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