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Diversity-generating retroelements (DGRs) create massive protein sequence variation (up to 1030)1in ecologically diverse microorganisms. A recent survey identified around 31,000 DGRs from more than 1,500 bacterial and archaeal genera, constituting more than 90 environment types2. DGRs are especially enriched in the human gut microbiome2,3and nano-sized microorganisms that seem to comprise most microbial life and maintain DGRs despite reduced genomes4,5. DGRs are also implicated in the emergence of multicellularity6,7. Variation occurs during reverse transcription of a protein-encoding RNA template coupled to misincorporation at adenosines. In the prototypical Bordetellabacteriophage DGR, the template must be surrounded by upstream and downstream RNA segments for complementary DNA synthesis to be carried out by a complex of the DGR reverse transcriptase bRT and associated protein Avd. The function of the surrounding RNA was unknown. Here we show through cryogenic electron microscopy that this RNA envelops bRT and lies over the barrel-shaped Avd, forming an intimate ribonucleoprotein. An abundance of essential interactions in the ribonucleoprotein precisely position an RNA homoduplex in the bRT active site for initiation of reverse transcription. Our results explain how the surrounding RNA primes complementary DNA synthesis, promotes processivity, terminates polymerization and strictly limits mutagenesis to specific proteins through mechanisms that are probably conserved in DGRs belonging to distant taxa.

The outbreak of clade 2.3.4.4b highly pathogenic avian influenza viruses of the H5N1 subtype (HPAI H5N1) in dairy cattle in the USA has so far resulted in spillover infections of at least 14 farm workers1, 2–3, who presented with mild respiratory symptoms or conjunctivitis, and one individual with no known animal exposure who was hospitalized but recovered3,4. Here we characterized A/Texas/37/2024 (huTX37-H5N1), a virus isolated from the eyes of an infected farm worker who developed conjunctivitis5. huTX37-H5N1 replicated efficiently in primary human alveolar epithelial cells, but less efficiently in corneal epithelial cells. Despite causing mild disease in the infected worker, huTX37-H5N1 proved lethal in mice and ferrets and spread systemically, with high titres in both respiratory and non-respiratory organs. Importantly, in four independent experiments in ferrets, huTX37-H5N1 transmitted by respiratory droplets in 17–33% of transmission pairs, and five of six exposed ferrets that became infected died. PB2-631L (encoded by bovine isolates) promoted influenza polymerase activity in human cells, suggesting a role in mammalian adaptation similar to that of PB2-627K (encoded by huTX37-H5N1). In addition, bovine HPAI H5N1 virus was found to be susceptible to polymerase inhibitors both in vitro and in mice. Thus, HPAI H5N1 virus derived from dairy cattle transmits by respiratory droplets in mammals without previous adaptation and causes lethal disease in animal models.

Making payments directly to farmers can encourage them to use fertilizer more wisely, thereby improving soil health, yields and the environment.

Undesired coupling to the surrounding environment destroys long-range correlations in quantum processors and hinders coherent evolution in the nominally available computational space. This noise is an outstanding challenge when leveraging the computation power of near-term quantum processors1. It has been shown that benchmarking random circuit sampling with cross-entropy benchmarking can provide an estimate of the effective size of the Hilbert space coherently available2–8. Nevertheless, quantum algorithms’ outputs can be trivialized by noise, making them susceptible to classical computation spoofing. Here, by implementing an algorithm for random circuit sampling, we demonstrate experimentally that two phase transitions are observable with cross-entropy benchmarking, which we explain theoretically with a statistical model. The first is a dynamical transition as a function of the number of cycles and is the continuation of the anti-concentration point in the noiseless case. The second is a quantum phase transition controlled by the error per cycle; to identify it analytically and experimentally, we create a weak-link model, which allows us to vary the strength of the noise versus coherent evolution. Furthermore, by presenting a random circuit sampling experiment in the weak-noise phase with 67 qubits at 32 cycles, we demonstrate that the computational cost of our experiment is beyond the capabilities of existing classical supercomputers. Our experimental and theoretical work establishes the existence of transitions to a stable, computationally complex phase that is reachable with current quantum processors.

Highly pathogenic H5N1 avian influenza (HPAI H5N1) viruses occasionally infect, but typically do not transmit, in mammals. In the spring of 2024, an unprecedented outbreak of HPAI H5N1 in bovine herds occurred in the USA, with virus spread within and between herds, infections in poultry and cats, and spillover into humans, collectively indicating an increased public health risk1–4. Here we characterize an HPAI H5N1 virus isolated from infected cow milk in mice and ferrets. Like other HPAI H5N1 viruses, the bovine H5N1 virus spread systemically, including to the mammary glands of both species, however, this tropism was also observed for an older HPAI H5N1 virus isolate. Bovine HPAI H5N1 virus bound to sialic acids expressed in human upper airways and inefficiently transmitted to exposed ferrets (one of four exposed ferrets seroconverted without virus detection). Bovine HPAI H5N1 virus thus possesses features that may facilitate infection and transmission in mammals.

Ultracold polyatomic molecules offer opportunities1in cold chemistry2,3, precision measurements4and quantum information processing5,6, because of their rich internal structure. However, their increased complexity compared with diatomic molecules presents a challenge in using conventional cooling techniques. Here we demonstrate an approach to create weakly bound ultracold polyatomic molecules by electroassociation7(F.D. et al., manuscript in preparation) in a degenerate Fermi gas of microwave-dressed polar molecules through a field-linked resonance8–11. Starting from ground-state NaK molecules, we create around 1.1 × 103weakly bound tetratomic (NaK)2molecules, with a phase space density of 0.040(3) at a temperature of 134(3) nK, more than 3,000 times colder than previously realized tetratomic molecules12. We observe a maximum tetramer lifetime of 8(2) ms in free space without a notable change in the presence of an optical dipole trap, indicating that these tetramers are collisionally stable. Moreover, we directly image the dissociated tetramers through microwave-field modulation to probe the anisotropy of their wavefunction in momentum space. Our result demonstrates a universal tool for assembling weakly bound ultracold polyatomic molecules from smaller polar molecules, which is a crucial step towards Bose–Einstein condensation of polyatomic molecules and towards a new crossover from a dipolar Bardeen–Cooper–Schrieffer superfluid13–15to a Bose–Einstein condensation of tetramers. Moreover, the long-lived field-linked state provides an ideal starting point for deterministic optical transfer to deeply bound tetramer states16–18.

In recent years, the stacking and twisting of atom-thin structures with matching crystal symmetry has provided a unique way to create new superlattice structures in which new properties emerge1,2. In parallel, control over the temporal characteristics of strong light fields has allowed researchers to manipulate coherent electron transport in such atom-thin structures on sublaser-cycle timescales3,4. Here we demonstrate a tailored light-wave-driven analogue to twisted layer stacking. Tailoring the spatial symmetry of the light waveform to that of the lattice of a hexagonal boron nitride monolayer and then twisting this waveform result in optical control of time-reversal symmetry breaking5and the realization of the topological Haldane model6in a laser-dressed two-dimensional insulating crystal. Further, the parameters of the effective Haldane-type Hamiltonian can be controlled by rotating the light waveform, thus enabling ultrafast switching between band structure configurations and allowing unprecedented control over the magnitude, location and curvature of the bandgap. This results in an asymmetric population between complementary quantum valleys that leads to a measurable valley Hall current7, which can be detected by optical harmonic polarimetry. The universality and robustness of our scheme paves the way to valley-selective bandgap engineering on the fly and unlocks the possibility of creating few-femtosecond switches with quantum degrees of freedom.

The human microbiome encodes a large repertoire of biochemical enzymes and pathways, most of which remain uncharacterized. Here, using a metagenomics-based search strategy, we discovered that bacterial members of the human gut and oral microbiome encode enzymes that selectively phosphorylate a clinically used antidiabetic drug, acarbose1,2, resulting in its inactivation. Acarbose is an inhibitor of both human and bacterial α-glucosidases3, limiting the ability of the target organism to metabolize complex carbohydrates. Using biochemical assays, X-ray crystallography and metagenomic analyses, we show that microbiome-derived acarbose kinases are specific for acarbose, provide their harbouring organism with a protective advantage against the activity of acarbose, and are widespread in the microbiomes of western and non-western human populations. These results provide an example of widespread microbiome resistance to a non-antibiotic drug, and suggest that acarbose resistance has disseminated in the human microbiome as a defensive strategy against a potential endogenous producer of a closely related molecule.

Intensive irrigation and climate change are depleting groundwater reserves in this fast-developing nation. To improve its water security, researchers need more information on water use, quality, flows and forecasts.

Lung cancer is the leading cause of cancer-associated mortality worldwide1. Here we analysed 1,644 tumour regions sampled at surgery or during follow-up from the first 421 patients with non-small cell lung cancer prospectively enrolled into the TRACERx study. This project aims to decipher lung cancer evolution and address the primary study endpoint: determining the relationship between intratumour heterogeneity and clinical outcome. In lung adenocarcinoma, mutations in 22 out of 40 common cancer genes were under significant subclonal selection, including classical tumour initiators such as TP53and KRAS. We defined evolutionary dependencies between drivers, mutational processes and whole genome doubling (WGD) events. Despite patients having a history of smoking, 8% of lung adenocarcinomas lacked evidence of tobacco-induced mutagenesis. These tumours also had similar detection rates for EGFRmutations and for RET, ROS1, ALKand METoncogenic isoforms compared with tumours in never-smokers, which suggests that they have a similar aetiology and pathogenesis. Large subclonal expansions were associated with positive subclonal selection. Patients with tumours harbouring recent subclonal expansions, on the terminus of a phylogenetic branch, had significantly shorter disease-free survival. Subclonal WGD was detected in 19% of tumours, and 10% of tumours harboured multiple subclonal WGDs in parallel. Subclonal, but not truncal, WGD was associated with shorter disease-free survival. Copy number heterogeneity was associated with extrathoracic relapse within 1 year after surgery. These data demonstrate the importance of clonal expansion, WGD and copy number instability in determining the timing and patterns of relapse in non-small cell lung cancer and provide a comprehensive clinical cancer evolutionary data resource.

Circulating tumour DNA (ctDNA) can be used to detect and profile residual tumour cells persisting after curative intent therapy1. The study of large patient cohorts incorporating longitudinal plasma sampling and extended follow-up is required to determine the role of ctDNA as a phylogenetic biomarker of relapse in early-stage non-small-cell lung cancer (NSCLC). Here we developed ctDNA methods tracking a median of 200 mutations identified in resected NSCLC tissue across 1,069 plasma samples collected from 197 patients enrolled in the TRACERx study2. A lack of preoperative ctDNA detection distinguished biologically indolent lung adenocarcinoma with good clinical outcome. Postoperative plasma analyses were interpreted within the context of standard-of-care radiological surveillance and administration of cytotoxic adjuvant therapy. Landmark analyses of plasma samples collected within 120 days after surgery revealed ctDNA detection in 25% of patients, including 49% of all patients who experienced clinical relapse; 3 to 6 monthly ctDNA surveillance identified impending disease relapse in an additional 20% of landmark-negative patients. We developed a bioinformatic tool (ECLIPSE) for non-invasive tracking of subclonal architecture at low ctDNA levels. ECLIPSE identified patients with polyclonal metastatic dissemination, which was associated with a poor clinical outcome. By measuring subclone cancer cell fractions in preoperative plasma, we found that subclones seeding future metastases were significantly more expanded compared with non-metastatic subclones. Our findings will support (neo)adjuvant trial advances and provide insights into the process of metastatic dissemination using low-ctDNA-level liquid biopsy.

Scattering resonances are an essential tool for controlling the interactions of ultracold atoms and molecules. However, conventional Feshbach scattering resonances1, which have been extensively studied in various platforms1–7, are not expected to exist in most ultracold polar molecules because of the fast loss that occurs when two molecules approach at a close distance8–10. Here we demonstrate a new type of scattering resonance that is universal for a wide range of polar molecules. The so-called field-linked resonances11–14occur in the scattering of microwave-dressed molecules because of stable macroscopic tetramer states in the intermolecular potential. We identify two resonances between ultracold ground-state sodium–potassium molecules and use the microwave frequencies and polarizations to tune the inelastic collision rate by three orders of magnitude, from the unitary limit to well below the universal regime. The field-linked resonance provides a tuning knob to independently control the elastic contact interaction and the dipole–dipole interaction, which we observe as a modification in the thermalization rate. Our result provides a general strategy for resonant scattering between ultracold polar molecules, which paves the way for realizing dipolar superfluids15and molecular supersolids16, as well as assembling ultracold polyatomic molecules.

Population isolates such as those in Finland benefit genetic research because deleterious alleles are often concentrated on a small number of low-frequency variants (0.1% ≤ minor allele frequency < 5%). These variants survived the founding bottleneck rather than being distributed over a large number of ultrarare variants. Although this effect is well established in Mendelian genetics, its value in common disease genetics is less explored1,2. FinnGen aims to study the genome and national health register data of 500,000 Finnish individuals. Given the relatively high median age of participants (63 years) and the substantial fraction of hospital-based recruitment, FinnGen is enriched for disease end points. Here we analyse data from 224,737 participants from FinnGen and study 15 diseases that have previously been investigated in large genome-wide association studies (GWASs). We also include meta-analyses of biobank data from Estonia and the United Kingdom. We identified 30 new associations, primarily low-frequency variants, enriched in the Finnish population. A GWAS of 1,932 diseases also identified 2,733 genome-wide significant associations (893 phenome-wide significant (PWS), P< 2.6 × 10–11) at 2,496 (771 PWS) independent loci with 807 (247 PWS) end points. Among these, fine-mapping implicated 148 (73 PWS) coding variants associated with 83 (42 PWS) end points. Moreover, 91 (47 PWS) had an allele frequency of <5% in non-Finnish European individuals, of which 62 (32 PWS) were enriched by more than twofold in Finland. These findings demonstrate the power of bottlenecked populations to find entry points into the biology of common diseases through low-frequency, high impact variants.

The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics and the properties of the proton’s bound state. A fundamental property of the proton involves the response of the system to an external electromagnetic field. It is characterized by the electromagnetic polarizabilities1that describe how easily the charge and magnetization distributions inside the system are distorted by the electromagnetic field. Moreover, the generalized polarizabilities2map out the resulting deformation of the densities in a proton subject to an electromagnetic field. They disclose essential information about the underlying system dynamics and provide a key for decoding the proton structure in terms of the theory of the strong interaction that binds its elementary quark and gluon constituents. Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved for two decades2. Here we report measurements of the proton’s electromagnetic generalized polarizabilities at low four-momentum transfer squared. We show evidence of an anomaly to the behaviour of the proton’s electric generalized polarizability that contradicts the predictions of nuclear theory and derive its signature in the spatial distribution of the induced polarization in the proton. The reported measurements suggest the presence of a new, not-yet-understood dynamical mechanism in the proton and present notable challenges to the nuclear theory.

Quantum error correction protects fragile quantum information by encoding it into a larger quantum system1,2. These extra degrees of freedom enable the detection and correction of errors, but also increase the control complexity of the encoded logical qubit. Fault-tolerant circuits contain the spread of errors while controlling the logical qubit, and are essential for realizing error suppression in practice3–6. Although fault-tolerant design works in principle, it has not previously been demonstrated in an error-corrected physical system with native noise characteristics. Here we experimentally demonstrate fault-tolerant circuits for the preparation, measurement, rotation and stabilizer measurement of a Bacon–Shor logical qubit using 13 trapped ion qubits. When we compare these fault-tolerant protocols to non-fault-tolerant protocols, we see significant reductions in the error rates of the logical primitives in the presence of noise. The result of fault-tolerant design is an average state preparation and measurement error of 0.6 per cent and a Clifford gate error of 0.3 per cent after offline error correction. In addition, we prepare magic states with fidelities that exceed the distillation threshold7, demonstrating all of the key single-qubit ingredients required for universal fault-tolerant control. These results demonstrate that fault-tolerant circuits enable highly accurate logical primitives in current quantum systems. With improved two-qubit gates and the use of intermediate measurements, a stabilized logical qubit can be achieved.

Letter to the Editor

Letter to the Editor

Resistance represents a major challenge for antibody-based therapy for COVID-191–4. Here we engineered an immunoglobulin M (IgM) neutralizing antibody (IgM-14) to overcome the resistance encountered by immunoglobulin G (IgG)-based therapeutics. IgM-14 is over 230-fold more potent than its parental IgG-14 in neutralizing SARS-CoV-2. IgM-14 potently neutralizes the resistant virus raised by its corresponding IgG-14, three variants of concern—B.1.1.7 (Alpha, which first emerged in the UK), P.1 (Gamma, which first emerged in Brazil) and B.1.351 (Beta, which first emerged in South Africa)—and 21 other receptor-binding domain mutants, many of which are resistant to the IgG antibodies that have been authorized for emergency use. Although engineering IgG into IgM enhances antibody potency in general, selection of an optimal epitope is critical for identifying the most effective IgM that can overcome resistance. In mice, a single intranasal dose of IgM-14 at 0.044 mg per kg body weight confers prophylactic efficacy and a single dose at 0.4 mg per kg confers therapeutic efficacy against SARS-CoV-2. IgM-14, but not IgG-14, also confers potent therapeutic protection against the P.1 and B.1.351 variants. IgM-14 exhibits desirable pharmacokinetics and safety profiles when administered intranasally in rodents. Our results show that intranasal administration of an engineered IgM can improve efficacy, reduce resistance and simplify the prophylactic and therapeutic treatment of COVID-19.

Gene-editing technologies, which include the CRISPR–Cas nucleases1–3and CRISPR base editors4,5, have the potential to permanently modify disease-causing genes in patients6. The demonstration of durable editing in target organs of nonhuman primates is a key step before in vivo administration of gene editors to patients in clinical trials. Here we demonstrate that CRISPR base editors that are delivered in vivo using lipid nanoparticles can efficiently and precisely modify disease-related genes in living cynomolgus monkeys (Macaca fascicularis). We observed a near-complete knockdown of PCSK9in the liver after a single infusion of lipid nanoparticles, with concomitant reductions in blood levels of PCSK9 and low-density lipoprotein cholesterol of approximately 90% and about 60%, respectively; all of these changes remained stable for at least 8 months after a single-dose treatment. In addition to supporting a ‘once-and-done’ approach to the reduction of low-density lipoprotein cholesterol and the treatment of atherosclerotic cardiovascular disease (the leading cause of death worldwide7), our results provide a proof-of-concept for how CRISPR base editors can be productively applied to make precise single-nucleotide changes in therapeutic target genes in the liver, and potentially in other organs.

Most ovarian cancers are infiltrated by prognostically relevant activated T cells1–3, yet exhibit low response rates to immune checkpoint inhibitors4. Memory B cell and plasma cell infiltrates have previously been associated with better outcomes in ovarian cancer5,6, but the nature and functional relevance of these responses are controversial. Here, using 3 independent cohorts that in total comprise 534 patients with high-grade serous ovarian cancer, we show that robust, protective humoral responses are dominated by the production of polyclonal IgA, which binds to polymeric IgA receptors that are universally expressed on ovarian cancer cells. Notably, tumour B-cell-derived IgA redirects myeloid cells against extracellular oncogenic drivers, which causes tumour cell death. In addition, IgA transcytosis through malignant epithelial cells elicits transcriptional changes that antagonize the RAS pathway and sensitize tumour cells to cytolytic killing by T cells, which also contributes to hindering malignant progression. Thus, tumour-antigen-specific and -antigen-independent IgA responses antagonize the growth of ovarian cancer by governing coordinated tumour cell, T cell and B cell responses. These findings provide a platform for identifying targets that are spontaneously recognized by intratumoural B-cell-derived antibodies, and suggest that immunotherapies that augment B cell responses may be more effective than approaches that focus on T cells, particularly for malignancies that are resistant to checkpoint inhibitors.

The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor1. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space. Here we report the use of a processor with programmable superconducting qubits2–7to create quantum states on 53 qubits, corresponding to a computational state-space of dimension 253(about 1016). Measurements from repeated experiments sample the resulting probability distribution, which we verify using classical simulations. Our Sycamore processor takes about 200 seconds to sample one instance of a quantum circuit a million times—our benchmarks currently indicate that the equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years. This dramatic increase in speed compared to all known classical algorithms is an experimental realization of quantum supremacy8–14for this specific computational task, heralding a much-anticipated computing paradigm.

Chaos is an inherent feature of many nonlinear systems. In particular, the transition from a steady to chaotic state occurs independently of the physical properties of the system. Such behaviour occurs in optics, both in lasers and in nonlinear optical devices. Such devices, which are fundamentally simple both in construction and in the mathematics that describes them, provide excellent opportunities for investigating nonlinear phenomena as well as for technological innovation.

WE report here the results of the measurements of the abundances of Ca, Ti and Cr nuclei relative to Fe, in low energy cosmic rays in 25–100 MeV/a.m.u. interval, which were measured in a dielectric detector assembly exposed on the outside of Skylab III for 73 d. The collecting power (defined as the product of area and exposure time) of the lexan detector in this experiment was the largest so far used in free space—1.1 × 109cm2s and the period of exposure from November 22, 1973 to February 3, 1974 was exceptionally ‘quiet’ (free from solar activity). These factors enabled us to make a reliable study of the abundance of these low energy cosmic-ray nuclei. The results on the measurements of the low energy oxygen group of nuclei in the same detector have been reported earlier1. We found an interesting feature in the enhanced abundances of low energy Ca–Cr nuclei relative to Fe, which are different from the composition of high energy (> 1 GeV/a.m.u.) cosmic rays, but are similar to those of low energy cosmic-ray nuclei observed in interplanetary space2,3. In the present work, however, observations have been made down to an energy of 25 MeV/a.m.u., which is a factor of two lower than those in earlier studies.

The epidermal growth factor (EGF) receptor and other growth factor receptors have been shown to possess tyrosine-specific protein kinase activity1–5. Before the demonstration of kinase activity in growth factor receptors, tyrosine kinases of molecular weight (MW) 60,000 (60K) were found to be encoded by the src oncogene and other oncogenes related to src6–8. Our earlier work on intracellular processing of the EGF receptor9, a 170,000-MW polypeptide, provided evidence for proteolytic separation of well defined structural domains, and suggested to us the possibility of separating functional domains by limited proteolysis. The isolation of such kinase domains should facilitate comparison of the receptor/kinase with other well characterized kinases including those of oncogene origin. We report here the identification of a catalytically functional 42K kinase derived proteolytically from the isolated human EGF receptor. This fragment, comparable in size to pp60src, carries the kinase ATP-binding site, and functions catalytically even after detachment from the EGF-binding site and the major autophosphorylation region.

α2uGLOBULIN is an androgen-dependent rat urinary protein with a molecular weight of about 23,800 (ref. 1). In the male rat, starting from puberty until senescence, α2uglobulin is synthesised and secreted by the hepatic tissue and is rapidly cleared by the kidneys into the urine2–4. In addition to its urinary concentration α2uglobulin has been found to be concentrated by the salivary glands and released into the saliva (A.K.R., and J.G.B., in preparation). Synthesis of this protein could be induced in the spayed female rat by androgen, and oestrogenic compounds completely inhibited α2usynthesis in the mature male rat5. But α2uglobulin does not bind testosterone, oestradiol-17β or any of their metabolites (unpublished results of A.K.R.). Pretreatment of mature male rats with oestrogen induces a dose-dependent temporary lag period within which α2uglobulin is not synthesised even under androgenic stimulation. With a daily oestradiol dose of 50 µg per 100g body weight a lag period extending up to 3–4 weeks has been established6. Although the adult male rat synthesises 20–30 mg of α2uglobulin per day, no physiological role of this protein has yet been established. The close parallel between the male reproductive capability and the production of α2uglobulin4,5prompted us to look into the possible reproductive role of this protein. The discovery of the oestrogen-mediated lag period in the mature male rats also provided an opportunity to look into the spermatogenic abnormalities within this lag period and any reparative effects which α2uglobulin may have on such damage. The results reported here demonstrate considerable protection of spermatogenesis by α2uglobulin against potential damage by oestrogen.

WE report the observation of sudden changes in the intensity of Sco X-1 by a factor of about three in the energy interval 29.9–52.3 keV on December 22, 1968, between 0427 h and 0553 h UT. The observation was made with an X-ray telescope in a balloon flight from Hyderabad (latitude 17.6° N, longitude 78.5° E), India. The telescope consisted of an NaI(Tl) crystal with an area of 97.3 cm2and thickness 4 mm surrounded by both active and passive collimators. The passive collimator was a cylindrical graded shield of lead, tin and copper and the active collimator was a plastic scintillator surrounding the shield. The field of view of the telescope at f.w.h.m. was 18.6°. The axis of the telescope was inclined at an angle of 32° to the zenith. The telescope was mounted on an oriented platform programmed to look in four specified directions successively, spending about 4 min in each direction during a cycle of period about 16 min. The four specified directions were N(ϕ = 0), SW(ϕ=110°, with the convention ϕ = 90° being due west), S(ϕ = 180°, due south) and NE(ϕ = 310°). In this flight the orienter performed satisfactorily and the telescope picked up Sco X-1 in the south direction, Cyg X-1 in the direction NE(ϕ = 310°) and a new source in the direction SW(ϕ = 110°). In the north direction (ϕ = 0) there was no source during the period of observation and therefore the information on background X-rays was obtained from this direction. The observations of the short term changes of intensity of Sco X-1 are discussed here—the results from the other data will be published separately. A pair of crossed flux gate magnetometers provided information every 8.2 s on the azimuth of the telescope. The pulse heights from the X-ray detector were sorted into nine contiguous channels extending from 10 to 120 keV. Counting rates of several channels were combined for analysis to improve the statistics. A 241Am source came into the field of view of the telescope once in 15 min for about 30 s to provide in-flight calibration of the detector and this indicated that there was stable operation and no drift in the channel positions during the flight. The balloon was launched at 0200 h UT and reached the ceiling altitude at 0435 h. Between 0435 and 0530 h, the ceiling altitude was 7.6 ± 0.3 g cm−2. Just before the balloon reached the ceiling Sco X-1 was in the field of view of the telescope for 3 min 41 s when the balloon was ascending from 9.2 to 8.3 g cm−2. After the balloon reached ceiling, Sco X-1 was in the field of view on five occasions between 0443 and 0553 h. During the last observation, 0551–0553 h, however, the floating altitude of the balloon was a little lower, 8.5 g cm−2. The meridian transit of Sco X-1 was at 0454 h and the flight was terminated at 0615 h.

THE Volta Dam was closed on May 18, 1964, initiating the transformation of a tropical river into one of the largest man-made lakes in the world. This lake will lie between latitudes 6° N. and 9° N. along the 0° meridian. Stretching more than 250 miles, it will eventually cover an area of 3,275 square miles and hold 120 million ft./acre of water. The maximum elevation of the water surface will be maintained at 276 ft. above sea-level and the seasonal variation in depth will be 8–10 ft.

IN many cases the effectiveness of herbicides has been increased by the addition of surface active agents to the spray1–4, but little information is available about the effects of growth regulators on the uptake and metabolism of herbicides by foliage. The object of this work was to investigate the role of gibberellic acid (GA3) and indolyl-3-acetic acid (IAA) on the absorption, diffusion, transloca-tion, and metabolism of 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine) by the upper and lower surfaces of tea leaves, Camellia sinensis.

THERE is considerable difference of opinion regarding the possibility of the oxidation of nitrites by oxygen to nitrates. Berzelius reported that when aqueous solutions of alkali nitrites are boiled in air, they absorb oxygen with the formation of nitrates. G. Lunge and E. Frémy, J. Lang1and others showed that aqueous solutions of nitrites pass into nitrates. According to R. Abegg and H. Pick2, oxygen of the air oxidises a solution of silver nitrite to silver nitrate. On the other hand, E. Divers3, Sir P. C. Rây4, C. Russworm5, M. Oswald6, and others observed no oxidation of solutions of nitrites in air. C. Matignon and G. Marchal7reported that an aqueous solution of sodium nitrite is not oxidised by prolonged contact with oxygen, under a pressure of 50–55 atmospheres, even in the presence of a catalyst. But when the pressure is raised to 175 atmospheres and temperature to 395°–530°, solid sodium nitrite is almost completely oxidised to nitrate.

THE importance of kinetin and related compounds in controlling different physiological processes in higher plants has been widely recognized, although attempts to isolate and identify such substances in plant material have so far failed1. Chromatographic separation of pea seedling extract yielded some pertinent information which is reported here.

CALVIN and his co-workers1have suggested that 6,8-thioctic acid, the prosthetic group of pyruvic oxidase, is a key substance in photosynthesis, since the oxidized and reduced forms of this compound may control the distribution of the fixed carbon into the ‘true’ products of photosynthesis (for example, sugars) and the Krebs-cycle acids. It was proposed that thioctic acid is closely associated with the primary photochemical process2, and experimental evidence was advanced in support of the contention that thioctic acid increases the quantum efficiency of the Hill reaction in Scenedesmus3,4. This communication summarizes the results obtained in an investigation on whether the photosynthetic reduction of carbon dioxide also is stimulated by thioctic acid.

PASSIVE immunity is transmitted from mother to young in the rat, as in the mouse1, partly before birth, but chiefly after birth by way of the milk and the gut of the suckling. Postnatal transmission continues until the twentieth day of age2, when the capacity of the gut of the young rat to absorb antibody terminates although antibody continues to be secreted in the milk. The lactating female rat was chosen for investigating the transmission of antibody from the circulation to the milk.

THE available information regarding the chemical nature of nucleic acids in Cyanophyceae is very meagre, and deoxyribonucleic acid and ribonucleic acid have not been isolated chemically from this group. As the blue-green cell is peculiar in its nuclear structure, the chemical nature of its nucleic acids may be different in kind or degree from that of other sources. With this in view, the nucleic acids were isolated from Nostoc muscorum using the conventional method of Schmidt and Thannhauser as modified by Heinrich et al.1.

THE quenching of fluorescence in solution by added substances is generally regarded as an almost instantaneous process1. We have observed that a quenching process takes a considerable time for completion, affording thereby an opportunity of a very detailed study of the process. If an alcoholic solution of abietic acid be added to a solution of thionine in the same solvent, a slow and continuous decrease of fluorescence occurs until it is practically completely quenched. The change has been measured fluorimetrically, and a few typical results are represented graphically in Fig. 1.

THE physiology of flower initiation has been much investigated for more than half a century. It is now established that in conditions of inductive day length the leaves produce a hormone which induces differentiation in the apical meristem. The chemical nature of the hormone has not yet been definitely established. There have been many investigations of the effect of different organic compounds on plants in relation to flowering. The primary motive has been to look for compounds that could possess “florigenic” activity. Some workers have used various antimetabolites in an attempt to determine whether any of them block the synthesis of the floral stimulus, which could provide some indirect indications as to the nature of the hormone. Antimetabolite investigation has suggested that the flowering hormone may be a steroid or an isoprenoid-like compound1. Work on a strawberry variety has shown that unsaponifiable lipid fractions from flowering plants promote flowering in the vegetative ones2. The active substance may include vitamin E and certain unidentified sterols. This communication reports the effects of steroids on flowering of chrysanthemum plants in non-inductive conditions.

THE monolayers of long-chain compounds such as cetyl and stearyl alcohols are being used extensively to minimize the loss of water by evaporation in reserviors1. Permeability of water vapour through a monolayer depends on, among others, the magnitude of the van der Waals type of cohesive forces of the film molecule with its neighbours, and on the adhesive force between the monolayer and the water subphase. Further extension of the n-alkyl chain and/or suitable modification of the terminal polar group would, therefore, make a monolayer more effective in reducing evaporation.

SINCE Berthelot's classical work on the esterification of fatty acids with glycerol, in the last century, considerable work has been done on the topic1–4. The presence of 2-monoglyceride in technical products of glycerolysis has been reported recently5; this was not noticed by Feuge et al.4or by Becker et al.6on the ground that 2-monoglyceride is prone to be quickly isomerized to the more stable 1-monoglyceride at the high temperature of the reaction. The present work on the esterification of lauric, myristic, palmitic, stearic, oleic and linoleic acids with glycerol was undertaken to clarify the question of the formation of 2-monoglyceride in the esterification reaction mixture.

A PROJECT was undertaken to characterize the nucleic acids from Anacystis nidulans, a blue-green alga. The present communication deals with the characteristics of ribonucleic acid and a new cytidine compound from it.

CASHEW nut (Anacardium occidentale Linn.) shell liquid obtained from unroasted shells was found by Stadeler1to consist chiefly of anacardic acid (A) (on heating, this is decarboxylated to cardanol (B)), a salicylic acid derivative with a long unsaturated side-chain in the position ortho to the carboxyl group, and cardol (C), a resorcinol derivative with a similar side-chain. Smith2showed that the unbranched side-chain consisted of 15 carbon atoms and 2 double bonds ; other workers3have shown that the oily liquid is really a mixture of saturated and mono-, di-, and tri-olefinic compounds in proportions that give, on average, about two double bonds per molecule. Although the surface-active properties of the sulphonated shell liquid have already been studied4, no thorough investigation has yet been carried out on anacardic acid, which, being an arylalkyl surfactant and a promising bactericidal agent, needs special attention5. Results of a preliminary study on sodium anacardate as a surfactant and bactericidal agent are reported here. .

THE chemical nature of deoxyribonucleic acid in blue-green algæ was not known until very recently1–3. This communication deals with a quantitative study of deoxyribonueleic acid from Anacystis nidulans and its characterization in respect to that from other sources. Anacystis nidulans and Chlorella ellipsoidea were grown in continuous culture chambers as described earlier4,5. The algal cells were treated with cold 10 per cent trichloracetic acid, 95 per cent alcohol, alcohol/ether (3 : 1) and finally with ether until all the pigments except phycobilins were fully extracted. Deoxyribonucleic acid was isolated by one of the following procedures : (a) with 10 per cent sodium chloride (2 ml./ 10 mgm.) three times by refluxing at 80° C. for 1 hr. each time6; (b) with 1 N potassium hydroxide at room temperature7; (c) with 0.5 M perchloric acid8. Purification of deoxyribonueleic acid from protein and polysaccharide was done according to the methods described earlier9. Chromatographic analyses were done according to Wyatt10. Purines and pyrimidines were estimated by maximum extinction technique11. With different procedures of extraction it has been observed that the yield of purified deoxyribonucleic acid varies from 3.7 to 4.7 per cent of the dried cells after ether wash. The fresh weight of the cells was found to be 5 times that of the dried ether-washed cells and hence deoxyribonueleic acid constitutes 0.73–0.94 per cent of the fresh weight of the cells. Nitrogen content varies from 13.9 to 14.3 per cent and that of phosphorus from 6.8 to 8.2 per cent with different procedures of isolation. Deoxyribonucleic acid is found to have an absorption maximum at 257 mµ and minimum at 230 mµ The infra-red spectrum of deoxyribonueleic acid from Anacystis does not show any remarkable deviations from those of other sources. The main peaks are at 3, 6.1, 8.1 and 9.3–9.8µ The percentage of molar ratios of constituent bases, guanine, adenine, cytosine and thymine, in deoxyribonueleic acid of Anacystis was found to be 29.5, 23.3, 24.8, and 22.3 respectively. The ratios of G/C, A/T and Pu/Py were 1.19, 1.04 and 1.12 respectively. The average values only have been recorded here. The deviation of unity in base ratio in this case is very difficult to explain at present, though the presence of single-stranded deoxyribonueleic acid which has recently been isolated from bacteriophage12cannot be ruled out. The (A + T)/(G + C) ratio may be used as a species parameter. In the case of Anacystis nidulans this was found to be about 0.82.

CONSIDERABLE attention has lately been directed towards effective suppression of water evaporation from lakes and reservoirs by spreading insoluble monomolecular films over the water surfaces1,2. In order to be effective, the film-forming compound should have several desirable properties3such as : (i) low melting point (∼ 50° C.), which will enable it to spread rapidly on the water surface so that its monomolecular film, if damaged, is easily healed ; (ii) large equilibrium film pressure at the temperatures of water surfaces (15–40° C.) normally met with in practice ; (iii) the film formed should be stable, incompressible and condensed.