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Short-chain fatty acylations establish connections between cell metabolism and regulatory pathways. Lysine acetoacetylation (Kacac) was recently identified as a new histone mark. However, regulatory elements, substrate proteins, and epigenetic functions of Kacac are not yet fully understood, hindering further in-depth understanding of acetoacetate-modulated (patho)physiological processes. Here, we created a chemo-immunological approach for reliable detection of Kacac, and demonstrated that acetoacetate serves as the primary precursor for histone Kacac. We report the enzymatic addition of the Kacac mark by the acyltransferases GCN5, p300, and PCAF, and its removal by the deacetylase HDAC3. Furthermore, we establish acetoacetyl-CoA synthetase as a key regulator of cellular Kacac levels. A comprehensive proteomic analysis has identified 139 Kacac sites on 85 human proteins. Bioinformatics analysis of Kacac substrates and RNA sequencing data reveal the broad impacts of Kacac on multifaceted cellular processes. These findings unveil pivotal regulatory mechanisms for the acetoacetate-mediated Kacac pathway, opening a new avenue for further investigation into ketone body functions in various pathophysiological states. 

Abstract Gallium nitride (GaN) and aluminum nitride (AlN) host high-density two-dimensional electron and hole gases in undoped GaN quantum wells, created by built-in polarization fields and favorable band offsets. These interfacial states are essential for many high-power and high-frequency devices, yet momentum-resolved measurements (particularly under applied bias) remain rare due to two challenges: (i) the surface sensitivity of conventional vacuum-ultraviolet ARPES, which cannot probe deeply buried states, and (ii) the difficulty of implementing electrostatic gating in semiconductor heterostructures due to leakage currents. Here, we use soft X-ray ARPES to overcome the first challenge, directly accessing quantized states several nanometers below the surface in GaN/AlN heterostructures and relating their subband dispersions to transport characteristics. As a precursor to gated ARPES, we employ controlled oxygen adsorption to chemically tune the potential and track the resulting band shifts. This approach opens a pathway toward fully gate-tunable, momentum-resolved studies of buried states in wide-bandgap devices. 

We address the problem of active logistic regression in the realizable setting. It is well known that active learning can require exponentially fewer label queries compared to passive learning, in some cases using $$\log \frac{1}{\eps}$$ rather than $$\poly(1/\eps)$$ labels to get error $$\eps$$ larger than the optimum. We present the first algorithm that is polynomially competitive with the optimal algorithm on every input instance, up to factors polylogarithmic in the error and domain size. In particular, if any algorithm achieves label complexity polylogarithmic in $$\eps$$, so does ours. Our algorithm is based on efficient sampling and can be extended to learn more general class of functions. We further support our theoretical results with experiments demonstrating performance gains for logistic regression compared to existing active learning algorithms. 

Abstract The technologies used in the manipulation of light can be used to do analogue simulations of physical systems with wave-like equations of motion. This analogy is maximized by the use of all the degrees of freedom of light. The Helmholtz equation in physical optics and the Schödinger equation in quantum mechanics share the same mathematical form. We use this connection to prepare non-diffracting optical beams representing the spatial and temporal dynamics of a nonlinear physical system: the quantum pendulum. By using the propagation coordinate to represent time in the quantum problem, we are able to analogue-simulate quantum wavepacket dynamics. These manifest themselves in novel optical beams with rich three-dimensional structures, such as rotation and sloshing of the light’s intensity as it propagates. Our experimental results agree very well with the predictions from quantum theory, thus demonstrating that our system can be used as a platform to simulate the quantum pendulum dynamics. This three-dimensional light-sculpting capability has the potential to impact fields such as manipulation with light and imaging.