Posner qubits: spin dynamics of entangled Ca9(PO4)6 molecules and their role in neural processing

Real-Time Monitoring of Hydrolysis Reactions of Pyrophosphates with Dissolution Dynamic Nuclear Polarization

Dissolution dynamic nuclear polarization (d-DNP) has enabled applications such as the real-time monitoring of chemical reactions. Such applications are mainly for 13C and 15N spins with long spin-lattice relaxation times in the molecules of interest. However, the only applications for phosphorus using d-DNP are pH imaging and nucleation during crystallization due to the short relaxation times. Here we show that it is possible to observe enzyme reactions using d-DNP with phosphorus. Hyperpolarized 31P spins in pyrophosphate were obtained using bullet-DNP, which requires less dilution of highly polarized solid samples. Real-time monitoring of the hydrolysis reaction of pyrophosphate by inorganic pyrophosphatase from baker's yeast at physiological pH and was successfully achieved and the reaction rate was determined. This is an important reaction for a wide range of applications related to medicine, agriculture, and quantum life science.

The Biological Qubit: Calcium Phosphate Dimers, Not Trimers

The Posner molecule (calcium phosphate trimer, Ca₉(PO₄)₆) has been hypothesized to function as a biological quantum information processor due to its supposedly long-lived entangled ³¹P nuclear spin states. This hypothesis was challenged by our recent finding that the molecule lacks a well-defined rotational axis of symmetry─an essential assumption in the proposal for Posner-mediated neural processing─and exists as an asymmetric dynamical ensemble. Following up, we investigate here the spin dynamics of the molecule's entangled ³¹P nuclear spins within the asymmetric ensemble. Our simulations show that entanglement between two nuclear spins prepared in a Bell state in separate Posner molecules decays on a subsecond time scale─much faster than previously hypothesized, and not long enough for supercellular neuronal processing. Calcium phosphate dimers (Ca₆(PO₄)₄) however, are found to be surprisingly resilient to decoherence and are able to preserve entangled nuclear spins for hundreds of seconds, suggesting that neural processing might occur through them instead.

The Dynamical Ensemble of the Posner Molecule Is Not Symmetric

The Posner molecule, Ca₉(PO₄)₆, has long been recognized to have biochemical relevance in various physiological processes. It has found recent attention for its possible role as a biological quantum information processor, whereby the molecule purportedly maintains long-lived nuclear spin coherences among its ³¹P nuclei (presumed to be symmetrically arranged), allowing it to function as a room temperature qubit. The structure of the molecule has been of much dispute in the literature, although the S₆ point group symmetry has often been assumed and exploited in calculations. Using a variety of simulation techniques (including ab initio molecular dynamics and structural relaxation), rigorous data analysis tools, and by exploring thousands of individual configurations, we establish that the molecule predominantly assumes low-symmetry structures (C_s and C_i) at room temperature, as opposed to the higher-symmetry configurations explored previously. Our findings have important implications for the viability of this molecule as a qubit.

Waiting for Aπαταω: 250 Years Later

Scientific articles have been traditionally written from single points of view. In contrast, new knowledge is derived strictly from a dialectical process, through interbreeding of partially disparate perspectives. Dialogues, therefore, present a more veritable form for representing the process behind knowledge creation. They are also less prone to dogmatically disseminate ideas than monologues, alongside raising awareness of the necessity for discussion and challenging of differing points of view, through which knowledge evolves. Here we celebrate 250 years since the discovery of the chemical identity of the inorganic component of bone in 1769 by Johan Gottlieb Gahn through one such imaginary dialogue between two seasoned researchers and aficionados of this material. We provide the statistics on ups and downs in the popularity of this material throughout the history and also discuss important achievements and challenges associated with it. The shadow of Samuel Beckett's Waiting for Godot is cast over the dialogue, acting as its frequent reference point and the guide. With this dialogue presented in the format of a play, we provide hope that conversational or dramaturgical compositions of scientific articles - albeit virtually prohibited from the scientific literature of the day - may become more pervasive in the future.