多变鱼腥藻Mn^2＋,Ca^2＋和Mg^2＋之间取代作用和放氧的研究

借助于电子顺磁共振波谱仪(EPR)探测了多变鱼腥藻中 Mn~(2 )含量的变化。较高浓度的 CaCl_2和 Ca(NO_3),处理引起藻体中结合态 Mn 的游离和藻的放氧活性的下降。当结合Mn 游离量达57％时,放氧活性降为零。MgCl_2处理的效果小于 CaCl_2。较高浓度的 MnCl_2像 EGTA 一样抑制藻的放氧。与对照比较,在 CaCl_2、MgCl_2和 MnCl_2处理下藻体的低温荧光发射光谱发生变化,波长686nm处的肩消失,F_(130)/F_(695)比值下降。本文对光合放氧复合物中离子间可能在其结合位点上发生竞争性取代作用进行了讨论。     

Effect of a constant supply of different nitrogen sources on protein and carbohydrate content and enzyme activities of Anabaena variabilis cells

The effect of the nitrogen source on carbohydrate and protein contents and on several enzymatic activities involved in the carbon and nitrogen metabolism was studied in Anabaena variabilis ATCC 29413 cells grown under a constant supply of either N, NO⁻₃ or NH⁺₄ at different concentrations. An enhancement of protein content accompanied by a parallel decrease of carbohydrates was observed with increasing NO⁻₃ or NH⁺₄ concentrations in the medium. In cultures containing 0.1 m M NO⁻₃ or 0.1 m M NH⁺₄ nitrogenase (EC 1.18.6.1) activity was 74 and 66%, respectively, of that found in N₂-grown cells. This activity was still present with 1 m M NO⁻₃ or 1 m M NH⁺₄ in the medium and even with 10 m M NO⁻₃, but it was completely inhibited by 5 m M NH⁺₄. Ferredoxin-nitrate reductase (EC 1.7.7.2) activity was detected only in NO⁻₃ grown cells and simultaneously with nitrogenase activity. Increasing concentrations of combined nitrogen in the medium, especially NH⁺₄, promoted a concomitant decline of glutamine synthetase (EC 6.3.1.2), NADP⁺-isocitrate dehydrogenase (EC 1.1.1.42), and NAD⁺-malate dehydrogenase (EC 1.1.1.37) activities, suggesting that these enzymes play an important role in the regulation of carbon-nitrogen metabolism in cyanobacteria.     

Effect of Zn2+ on photosynthetic oxygen evolution and chloroplast manganese

Treatment of thylakoid suspensions with Zn²⁺ causes the appearance of an EPR signal due to Mn²⁺. The size of the signal was linearly correlated with the inhibition of oxygen evolution. Full inhibition appeared to correspond to the release of 2 Mn atoms/reaction centre of photosystem II. The released Mn²⁺ remained associated with the chloroplast pellet on centrifugation and took several hours to equilibrate with the surrounding medium. The sequestered Mn²⁺ does not appear to be in the thylakoid interior but in a more restricted hydrophilic compartment.     

The Effects of Immobilization on Photosynthesis,Growth, Nitrogen Fixation and Ammonium Ion Excretion of Mutant and Wild Type Cells of Anabaena variabilis

Ammonium ion photoproduced by nitrogen-fixing cyanobacteria is formed from water, air nitrogen and solar energy under normal temperature and atmospheric pressure. It is reported here that the mutant and its parent wiid type cells of Anabaena variabilis from Shanmugan lab were immobilized into the polyurethane foams. The growth curves measured by cell counting, O.D750 measurement and ch]orophyll a determination showed that the growth of the immobilized wild type cells was more rapid than the immobilized mutant cells, and for both two types of cells the free-living cells grew better than the immobilized ones. The nitrogenase activity (reduction of C2H2) was 44% greater in immobilized mutant cells and 232% greater in immobilized wild type cells than both free-living cells, respectively. Free-living cells of wild type A. variabilis almost did not excrete any ammonium ion and the immobilized cells of the wild type had the ammonium ion excretion activity similar to that of the free-living mutant cells. Moreover, immobilization stimulated the activity of ammonium ion excretion 55.6% greater than the free-living cells, in the mutant strain. The fluorescence enhancement induced by DCMU (3-(3,4-dichlor-benzene)-1, 1-dimethl urea) indicated the photosynthetic capability of wild type ceils in both free-living and immobilized states were higher than that of the mutant cells, and the free-living cells of both two types of cells had higher capability than the immobilized cells. The fluorescence emission spectra at 77K showed that there were four peak emission: F646(F645 or F650) and F662(F664 or F665) from phycobilin, F693(F698,F700 or F702) from PS Ⅱ and F732(F728 or F733 from PS Ⅰ In both two types of immobilized cells the photosynthetic light energy distribution tended to be in PS Ⅰ and it seems to be benefitlal for the nitrogenase activity and ammonium ion excretion. SEM observation indicated that the shape and size of the immobilized cells remained unchanged incompared with the free-living cells, However, the surface of the immobilized cells had accumulated some mucilage, and particularly, the film of mucilage coated both surface of the mutant cells and the foam matrix.     

The action of excessive,inorganic silicon (Si) on the mineral metabolism of calcium (Ca) and magnesium (Mg)

The influence of silicon treatment on the levels of calcium and magnesium in blood serum and tissues was studied in rats. The concentrations of both elements were estimated in samples of sera and tissues of rats receiving per os a soluble, inorganic silicon compound—sodium metasilicate nonahydrate (Na₂SiO₃·9H₂O (REACHIM, USSR)), dissolved in the animals' drinking water. A decrease of magnesium concentration in serum was observed with accompanying elevation of registered calcemia. Moreover, a reduction of tissue calcium levels was found with a simultaneous increase of magnesium tissue pool. The results provide evidence for silicon involvement in mineral metabolism. It could result in a modification of pathological processes concerning bone tissue.     

Ca2+ and Mg2+-binding and a putative calmodulin type Ca2+-binding site in Synechococcus Photosystem II

Thylakoids and Photosystem II particles prepared from the cyanobacterium Synechococcus PCC 7942 washed with a HEPES/glycerol buffer exhibited low rates of light-induced oxygen evolution. Addition of either Ca²⁺ or Mg²⁺ to both thylakoids and Photosystem II particles increased oxygen evolution independently, maximal rates being obtained by addition of both ions. If either preparation was washed with NaCl, light induced O₂ evolution was completely inhibited, but re-activated in the same manner by Ca²⁺ and Mg²⁺ but to a lower level. In the presence of Mg²⁺, the reactivation of O₂ evolution by Ca²⁺ allowed sigmoid kinetics, implying co-operative binding. The results are interpreted as indicating that not only Ca²⁺, but also Mg²⁺, is essential for light-induced oxygen evolution in thylakoids and Photosystem II particles from Synechococcus PC 7942. The significance of the reactivation kinetics is discussed. Reactivation by Ca²⁺ was inhibited by antibodies to mammalian calmodulin, indicating that the binding site in Photosystem II may be analogous to that of this protein.Abbreviation HEPES n-2-Hydroxyethylpiperazine--2-ethane sulphonic acid     

Properties of an ATP-dependent Ca2+ pump and (Ca2+ + Mg2+)-ATPase in brain synaptosome membrane vesicles from the bertha armyworm,Mamestra configurata Wlk

Biochemical and kinetic properties under identical substrate and reaction conditions were obtained for an ATP-dependent Ca²⁺ pump and (Ca²⁺ + Mg²⁺)-ATPase in synaptosome membrane vesicles prepared from the brain of the moth, Mamestra configurata. Both the ATP-dependent Ca²⁺ pump and (Ca²⁺ + Mg²⁺)-ATPase had single, high-affinity binding sites for ATP (K_m = 14 and 116 μM, respectively), Ca²⁺_free (K_m = 0.13 nM and 0.072 nM, respectively), and Mg²⁺ (K_m = 1.1 mM and 0.07 mM, respectively). Both systems were relatively little affected by K⁺ and were insensitive to ouabain, an inhibitor of (Na⁺ + K⁺)-ATPase. The results indicate that the ATP-dependent Ca²⁺ pump and (Ca²⁺ + Mg²⁺)-ATPase are functionally coupled in synaptic membranes and constitute a mechanism for Ca²⁺ transport in the brain of M. configurata. Although moth brain (Ca²⁺ + Mg²⁺)-ATPase is maximally active at nanomolar concentrations of free calcium ion, the enzyme retains at least one-half of its maximal activity at micromolar calcium concentrations, indicating either that the enzyme has two binding sites for calcium (a high-affinity site at nanomolar Ca²⁺_free and a low-affinity site at micromolar Ca²⁺_free), or that there are two enzymes with high and low affinity for calcium, respectively. Calcium extrusion from brain neurones of M. configurata may operate in a two-stage, concentration-dependent process in which a first stage, low-affinity pump reduces intraneuronal calcium to a concentration at which a second stage, high-affinity pump becomes activated.     

Effects of Ca2+, Mg2+, and depolarizing agents,on the32Pi-labeling and degradation of phosphatidylinositols in rat brain synaptosomes

In isolated synaptosomes from rat brain, 100 M antimycin A and 10 M oxamic acid inhibit the³²Pi-labeling of phosphatidylinositol-4,5-bisphosphate (PIP₂) and phosphatidylinositol-4-phosphate (PIP) by 90% and 95–99% respectively. 10 mM sodium fluoride inhibits the labeling by 50–60% and 10 mM A23187 inhibits the labeling by 63–70%. Phospholipase A₂ inhibits the labeling of PIP₂ and PIP by 93–94% and stimulates their degradation by 84–92%. Depolarization of synaptosomes with 75 mM K⁺ or 100 M veratrine decreases the labeling of PIP₂ and PIP by 66–74%. The decreased labeling results in large part from the Ca²⁺-dependent degradation of³²P-labeled PIP₂ and PIP as shown by pulse-chase experiments in which PIP₂ and PIP were prelabeled with³²Pi. Depolarization of synaptosomes results in the stimulation of⁴⁵Ca²⁺ uptake with the concomitant hydrolysis of PIP and PIP₂. Addition of 1 mM Ca²⁺ accounts for 25% of the enhanced degradation whereas depolarization with 75 mM K⁺ accounts for 75% of the enhanced degradation of PIP₂ and PIP. Depolarization with 100 mM veratrine results in a 223% increase in inositol trisphosphate as evidenced by stimulation of⁴⁵Ca²⁺ uptake. EGTA (10mM) and Mg²⁺ (5–10 mM) inhibit the degradation of PIP and PIP₂ and counteract the action of 1 mM Ca²⁺. Our data demonstrate that⁴⁵Ca²⁺, Mg²⁺, and membrane depolarization play an important role in the turnover of membrane phosphatidylinositols.Abbreviations ATP adenosine triphosphate - Pi inorganic orthophosphate - PIP phosphatidylinositol-4-phosphate - PIP₂ phosphatidylinositol-4,5,-bisphosphate - IP₃ inositol-1,4,5-trisphosphate     

Influence of different dietary calcium levels on the digestibility of Ca,Mg, and P in captive‐born juvenile Galapagos giant tortoises (Geochelone nigra)

Calcium (Ca) and phosphorus (P) are very important minerals in reptile nutrition, but many diets still are not balanced. To achieve optimal growth, including a healthy skeleton and a strong shell, a well‐balanced supply with these minerals is prerequisite. The purpose of this study was to evaluate the digestibility of diets with different calcium levels, with special emphasis on the digestibility of minerals. Fourteen captive‐born juvenile Galapagos giant tortoises of the Zurich and Rotterdam Zoos were used. The animals were housed indoors at a mean temperature of 23°C and 25°C, and at 65% and 60% humidity, respectively. The animals from the same zoo were fed the same diet, which consisted of vegetables, herbs, and a mixture of different Ca sources. Daily mixed fecal samples of all tortoises were collected from day 8 to day 18. A Weender analysis was performed and the HCl‐insoluble ash was used as an indigestible indicator (marker) for the determination of the apparent digestibility. The Ca content of the mixed feedstuffs of diet I was 1.43% on a dry matter basis, and the Ca:P ratio in the food was 3.9:1. In diet II, the Ca content was 2.06% on a dry matter basis, and the Ca:P ratio in the food was 4.8:1. Diet III contained 7.33% of Ca on a dry matter basis, and the Ca:P ratio in the food was 6.7:1. The digestibility of Ca in diet I was 42%. The other examined minerals, Mg and P, had a digestibility of 54% and 84%, respectively. In diet II, the digestibility of Ca was 63%, of Mg 76%, and of P 88%, and in diet III the digestibility of Ca was 82%, of Mg 92%, and of P 91%. The results of this study indicated that higher Ca concentrations in the diet led to an increased apparent digestibility of Ca, Mg, and P. The influence of an increased fat and decreased fiber content in diet III concerning digestibility is discussed. Zoo Biol 20:367–374, 2001. © 2001 Wiley‐Liss, Inc.     

Congeneric Serpentine and Nonserpentine Shrubs Differ More in Leaf Ca:Mg than in Tolerance of Low N, Low P, or Heavy Metals

Serpentine soils limit plant growth by NPK deficiencies, low Ca availability, excess Mg, and high heavy metal levels. In this study, three congeneric serpentine and nonserpentine evergreen shrub species pairs were grown in metalliferous serpentine soil with or without NPKCa fertilizer to test which soil factors most limit biomass production and mineral nutrition responses. Fertilization increased biomass production and allocation to leaves while decreasing allocation to roots in both serpentine and nonserpentine species. Simultaneous increases in biomass and leaf N:P ratios in fertilized plants of all six species suggest that N is more limiting than P in this serpentine soil. Neither N nor P concentrations, however, nor root to shoot translocation of these nutrients, differed significantly between serpentine and nonserpentine congeners. All six species growing in unfertilized serpentine soil translocated proportionately more P to leaves compared to fertilized plants, thus maintaining foliar P. Leaf Ca:Mg molar ratios of the nonserpentine species were generally equal to that of the soil. The serpentine species, however, maintained significantly higher leaf Ca:Mg than both their nonserpentine counterparts and the soil. Elevated leaf Ca:Mg in the serpentine species was achieved by selective Ca transport and/or Mg exclusion operating at the root-to-shoot translocation level, as root Ca and Mg concentrations did not differ between serpentine and nonserpentine congeners. All six species avoided shoot toxicity of heavy metals by root sequestration. The comparative data on nutrient deficiencies, leaf Ca:Mg, and heavy metal sequestration suggest that the ability to maintain high leaf Ca:Mg is a key evolutionary change needed for survival on serpentine soil and represents the physiological feature distinguishing the serpentine shrub species from their nonserpentine congeners. The results also suggest that high leaf Ca:Mg is achieved in these serpentine species by selective translocation of Ca and/or inhibited transport of Mg from roots, rather than by uptake/exclusion at root surfaces.     

Effects of aluminium on ATP pools and utilization in the cyanobacterium Anabaena cylindrica: a model for the in vivo toxicity

ATP pools extracted from the cyanobacterium Anabaena cylindrica , grown in the absence or presence of AlCl₃, were measured using the luciferin-luciferase assay. Addition of low concentrations of AlCl₃ (3.6–36 μ M ) increased the ATP pool 20–40% within 24 h, the effect being more marked with time. When using the Tris-EDTA boiling technique for extraction of cellular ATP, the ATP from aluminium-exposed cells appeared more stable during the extraction than the ATP from untreated cells. The higher ATP pools in aluminium-exposed cells were also evident after dark treatment and addition of the phosphorylating inhibitors carbonylcyanide m -chloro-phenylhydrazone (CCCP) and N,N-dicyclohexylcarbodiimide (DCCD). The formation of elevated ATP pools in cells exposed to aluminium was curtailed by high concentrations of cellular phosphate and postincubation at high pH (>8). These results favour the hypothesis that intracellular aluminium binds to ATP by competing with Mg²⁺ and, as a consequence, the stable Al³⁺-ATP complex formed is no longer available for cellular metabolism. The cyanobacterium is assumed to compensate by increasing the total pool of ATP. At high AlCl₃-concentrations, and in particular at low phosphate: aluminium molar ratios (<1), aluminium apparently also interferes with the membranes in A. cylindrica as indicated by inhibited O₂ production, reduced ATP production and cell lysis.     

Effects of chemical composition on N,Ca, and Mg release during incubation of leaves from selected agroforestry and fallow plant species

Nitrogen, Ca and Mg release from leaves of ten selected plant residues with varying chemical compositions was studied under laboratory conditions. Three patterns of N-release were observed over a seven week incubation period: (a)Gliricidia sepium, Leucaena leucocephala, Mucuna pruriens andCentrosema pubescens leaves showed rapid N release, (b)Acioa barteri andDialium guineense leaves immobilized N, and (c)Alchornea cordifolia, Anthonata macrophylla, Cassia siamea andPterocarpus santalinoides leaves initially showed N immobilization which gradually changes to net mineralization after about four weeks of incubation. Nitrogen mineralization rate constant (k) ranged from –0.0018 (A. barteri) to 0.0064 day^–1 (G. sepium). Statistical analysis of data showed that N mineralization rate constants are significantly correlated with initial N, polyphenol and lignin contents of leaves. Nitrogen release increased with increasing N content and decreased with increasing contents of polyphenols and lignin.Addition of leaves from all species significantly increased soil exchangeable Ca and Mg levels.L. leucocephala, G. sepium, C. pubescens andM. pruriens showed relatively high Ca and Mg release rates. Calcium release rate was related to N release rate rather than to initial Ca content.     

Influence of culture density,pH, organic acids and divalent cations on the removal of nutrients and metals by immobilized Anabaena doliolum and Chlorella vulgaris

The potential of alginate-immobilized Anabaena doliolum and Chlorella vulgaris was assessed for removal of nutrients (NO _inf3 ^sup- and NH _inf4 ^sup+ ) and metals (Cr₂O _inf7 ^sup2- and Ni²⁺) at different biomass concentrations (0.05, 0.1, 0.25, 0.49 and 1.22 g dry wt l^-1) and pH values (4 to 10). Though uptake of all these substances was higher in concentrated algal beads (0.25, 0.49 and 1.22 g dry wt l^-1), their rate of uptake was significantly (P<0.001) lower than that of low (0.05 g dry wt l^-1) cell density beads. For A. doliolum, there was no significant difference in uptake rates for beads having densities of 0.05 and 0.1 g dry wt l^-1. Chlorella vulgaris, however, showed maximum efficiency at 0.1 g dry wt l^-1. Uptake of both the nutrients and the metals was maximal at pH 7 followed by pH 8, 6, 9, 10, 5 and 4. Of the different substances (organic acids and divalent cations) used, humic acid was most efficient in decreasing metal uptake. Mg²⁺ was, however, more efficient than Ca²⁺ in decreasing Ni²⁺ uptake. Immobilized algae with a cell density of 0.1 g dry wt l^-1 were the most efficient for nutrient and metal removal at pH 6 to 8.     

Effect of Mg, Sr, and Mn on the chemico-physical and in vitro biological properties of calcium phosphate biomimetic coatings

We previously developed a calcium phosphate (CaP) calcifying solution that allows to deposit a uniform layer of nanocrystalline apatite on metallic implants in a few hours. In this work we modified the composition of the CaP solution by addition of Sr²⁺, Mg²⁺, and Mn²⁺, in order to improve the biological performance of the implants. The results of the investigation performed on the coatings, as well as on the powders precipitated in the absence of the substrates, indicate that both Sr²⁺ and Mg²⁺ reduce the extent of precipitation, although they are quantitatively incorporated into the nanocrystalline apatitic phase. The inhibitory effect on deposition is much more evident for Mn²⁺, which completely hinders the precipitation of apatite and yields just a small amount of amorphous phosphate relatively rich in manganese content. Human osteoblast-like MG-63 cells cultured on the different materials show that the Mg²⁺ and Sr²⁺ apatitic coatings promote proliferation and expression of collagen type I, with respect to bare Ti and to the thin layer of amorphous phosphate obtained in the presence of Mn²⁺. However, the relatively high content of Mn²⁺ in the phosphate has a remarkable beneficial effect on osteocalcin production, which is even greater than that observed for Sr²⁺.     

The effect of soil nutrient availability on retranslocation of Ca,Mg and K from senescing sapwood in Atlantic white cedar

Nutrient resorption from senescing tissues increases plant nutrient-use efficiency, and may be an adaptation to nutrient limitation. In some tree species, retranslocation of nutrients from sapwood during heartwood formation is a comparable process. We measured Ca, Mg and K concentrations in Atlantic white cedar (Chamaecyparis thyoides) stemwood samples taken from two swamps in the northeastern United States and compared them to soil mineral nutrient availability at each site. We found that Ca, Mg and K concentrations were 60–700% higher in sapwood than in the immediately adjacent heartwood, indicating retranslocation of these nutrients from senescing sapwood. Sapwood nutrient concentrations were similar between the two sites. However, nutrient concentrations in the heartwood differed significantly between the sites, as did the relative degree of Ca and Mg retranslocation from senescing sapwood. We found these differences between sites to be inversely related to significant differences in exchangeable Ca, Mg and K as well as Al concentrations in the soil. These findings suggest that the degree of nutrient retranslocation from senescing sapwood may be influenced by soil nutrient availability. This revised version was published online in July 2006 with corrections to the Cover Date.     

The cyclic nucleotide-activated conductance in olfactory cilia: Effects of cytoplasmic Mg2+ and Ca2+

Summary Olfactory receptor neurons depolarize in response to odorants. This depolarization is mediated by an increase in intracellular cyclic AMP, which directly gates channels in the membranes of the neuronal cilia. Previous evidence suggests that a Ca²⁺ influx during the odorant response may ultimately play a role in terminating the response. One way Ca²⁺ inside the cell could terminate the odorant response would be to directly inhibit the cAMP-gated channels. In this report the effects of cytoplasmic Ca²⁺ and Mg²⁺ on the cAMP-activated current were measured in single olfactory cilia. Near the neuronal resting potential, cytoplasmic Ca²⁺ and Mg²⁺ only slightly reduced the cAMP-activated current. Even at high levels (1.0mm Ca²⁺ or 5.0mm Mg²⁺), the average inhibition was only around 20%. It is therefore unlikely that an influx of divalent cations terminates the odorant response by a direct effect on the cAMP-gated channels.     

Distribution of N,P, K,Ca, Mg,S, Zn,Fe, Mn and Cu in groundnut

Summary Concentration of N, P, K, Ca, Mg and S in summer groundnut crop was higher than in kharif while Zn, Fe, Mn and Cu contents were higher in summer crop. Kernel's N, P and Zn; Leaflet's Ca and Mn; Stem's K and Fe; Root's S and Cu and Petiole's Mg contents were highest. Shell's N, P, K, Mg, S, Zn and Cu; Kernel's Ca, Fe and Mn contents were the least. N, P, K, S, Zn and Cu concentrations decreased linearly as the crop grew. Ca, Mg, Fe and Mn concentrations did not display any distinct pattern. Ca concentration was positively correlated with pod yield in both the seasons.     

Influence of Ca/mg ratio on phytoextraction properties of Salix viminalis I. The effectiveness of Cd, Cu, Pb, and Zn bioaccumulation and plant growth

Phytoremediation and its efficiency--influenced by several factors-is prime concern in reduction of environment contamination with heavy metals. The aim of the study was to estimate in controlled conditions--in relation to the natural Ca/Mg ratio 4:1--the influence of different Ca/Mg ratios (1:1/4, 20:1, 1:10) on selected heavy metals (Cd, Cu, Pb, and Zn) accumulation efficiency shown by three morphological parts of Salix viminalis 'Cinamomea' (cane bark, shoots and roots). Accumulation of heavy metals in experimental conditions was significantly Ca/Mg ratio dependent, and occurred in the following order: 1:10 > 4:1 > 20:1 > 1:1/4. The highest accumulation under 0.5 mM solutions (as compared to 0.1 mM) was noted for copper and zinc, and the lowest for cadmium. Biometric parameters of Salix viminalis cuttings revealed the highest biomass productivity under 20:1 and 4:1 Ca/Mg ratios. In the case of shoot length increase, both metal concentration and kind of metal present in the solution were important. The results indicate that higher calcium ion concentration in solution (Ca/Mg 20:1) stimulates Salix viminalis growth by 3 fold when compared to other Ca/Mg ratio. It can be an important factor in remediation of the environment with this plant.     

Graphitic‐Shell Encapsulation of Metal Electrocatalysts for Oxygen Evolution,Oxygen Reduction,and Hydrogen Evolution in Alkaline Solution

Developing highly efficient, cost effective, and environmentally friendly electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is of interest for sustainable and clean energy technologies, including metal–air batteries and fuel cells. In this work, the screening of electrocatalytic activities of a series of single metallic iron, cobalt, and nickel nanoparticles and their binary and ternary alloys encapsulated in a graphitic carbon shell toward the OER, ORR, and HER in alkaline media is reported. Synthesis of these compounds proceeds by a two‐step sol–gel and carbothermal reduction procedure. Various ex situ characterizations show that with harsh electrochemical activation, the graphitic shell undergoes an electrochemical exfoliation. The modified electronic properties of the remaining graphene layers prevent their exfoliation, protect the bulk of the metallic cores, and participate in the electrocatalysis. The amount of near‐surface, higher‐oxidation‐state metals in the as‐prepared samples increases with electrochemical cycling, indicating that some metallic nanoparticles are not adequately encased within the graphite shell. Such surface oxide species provide secondary active sites for the electrocatalytic activities. The Ni–Fe binary system gives the most promising results for the OER, and the Co–Fe binary system shows the most promise for the ORR and HER.