Biomolecular computing systems principles, progress and pote(3)

者 none”的输出，构成了一个逻辑功能，细胞中不同的监测和控制应用程序可以通过系统的方法来构建分子逻辑电路。

These circuits, which are also known as digital or Boolean circuits, belong to ‘circuit-based’ models in which data pass through ‘wires’ between small computational units (known as ‘gates’) that perform simple operations (FIG. 2a,b). Circuit models resemble coupled chemical reactions, in which the concentrations of individual species are interpreted as their values, and individual interactions are compared to circuit wires.

这些电路，被称为数字电路或布尔电路，属于“基于电路”的模型，数据通过小计算单元（称为门）之间的线，进行简单的操作（图2a,b）。电路模型与对应的化学反应相似，其中单个物质的浓度看做他们的值，单个物质之间的相互作用相当于电路导线。

图 2-a

图 2-b

Notably, specially designed circuits and their molecular implementations can act as memory, which is a key component of many useful computations. Digital-circuit-inspired approaches to molecular computation include enzymatic cascade logic(FIG. 2c), a universal set of enzyme-based gates (FIG. 2d), transcription-based universal gates such as NAND and NOR (FIG. 2e) and normal-form circuits (FIG. 2f). Compartmentalizing gates in separate microbial strains and connecting them by diffusing small molecules has been proposed and tested as a way of controlling cell communities.

值得注意的是，专门设计的电路及其分子实现可以作为内存，是许多有用计算的关键组成部分。数字电路启发的分子计算的方法包括酶促级联逻辑（图2c），一个基于酶的门的通用集（图2d），基于转录的门如与非门和或非门（图2e）和标准形式的电路（图2f）。已经提出在独立的微生物菌株上相隔开的门，用扩散小分子连接他们，经测试可以作为一种控制细胞群落的方法。

图 2-c

图 2-d

图 2-e

图2-f

Logic circuits are an approximation of the chemical process because concentrations are continuous. Analogue circuits contain gates that compute simple non-Boolean functions such as addition, multiplication and integration. Biomolecular analogue circuits have been examined theoretically. Ideas about analogue biological computing were also explored in the context of artificial neural networks composed of neuron-like gates that weight, add and ‘digitize’ the inputs. Early theoretical works on their molecular implementation inspired quite different experimental systems, showcasing elements such as an ‘adder’ gate, whose output level is a sum of its inputs’ levels.

逻辑电路是化学过程的一种近似，因为浓度是连续的。模拟电路包含非布尔运算的门，像加法运算、乘法运算和集成。生物分子的模拟电路已经通过理论验证。模拟生物计算的思想也已经在人工神经网络的背景下探究过，包含像神经元一样的门，量化、加入并且数字化输入。分子实现的早期理论启发了完全不同的实验系统，展示了 “加法器”等原理，它的输出是输入的总和。

State machines 状态机 A second large class of models comprises state machines that manipulate discrete data units — symbols — that are stored on tapes (FIG. 3). The com-puter processes the symbols according to specific rules. Even though these models have traditionally been used to prove statements about computability, parallels to transcription and translation make them plausible inspiration for practical biomolecular computations. Successful experimental implementation has been achieved so far for simpler, read-only models, such as finite automata. Theoretical blueprints of molecular Turing machines suggest

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