Flow analysis in a biological system adopting the buffer capacitor concept.

The flow measurement of each component in each compartment is important in works on transport phenomena in a biological system. The method of flow measurement was studied adopting the capacitor concept derived from network thermodynamics.A biologically active component i in a compartment is defined as follows,

$\text{n}{}_{\mathrm{i}}\text{=n}{}_1\text{+n}{}_2\text{=c}{}_1\text{V+c}{}_2\text{V}$

where the total quantity ni consists of a measurable form n_i (free form, conc. c₁) and concealed form n₂ (conc, c₂). Capacitor for the species i of a compartment is defined as follows,

$\text{C=}\text{d}\text{n}{}_{\mathrm{i}}\text{d}\text{μ}{}_{\mathrm{i}}\text{=}\text{1+}\text{c}{}_2\text{c}{}_1\text{c}{}_1\text{dV}\text{dμ}{}_{\mathrm{i}}\text{+}\text{1+}\text{dc}{}_2\text{dc}{}_1\text{v}\text{dc}{}_1\text{dμ}{}_{\mathrm{i}}$

,

$\text{=Ac}{}_1\text{dV}\text{dμ}{}_{\mathrm{i}}\text{+BV}\text{d}\text{c}{}_1\text{d}\text{t}$

Thus flow of each component is expressed as,

$\text{J}{}_{\mathrm{i}}\text{=}\text{d}\text{n}{}_{\mathrm{i}}\text{d}{}_{\mathrm{i}}\text{=}\text{d}\text{n}{}_{\mathrm{i}}\text{dμ}{}_{\mathrm{i}}\text{dμ}\text{n}{}_{\mathrm{i}}\text{dt}\text{=C}\text{d}\text{μ}{}_{\mathrm{i}}\text{dt}$

,

$\text{=Ac}{}_1\text{d}\text{V}\text{dt}\text{+BV}\text{d}\text{c}{}_1\text{dt}$

Method of determination of capacitor coefficients A and B by titration experiment was also considered. For an experimental case, the capacitance for H⁺ of blood compartment was determined. The relationship between the capacitor concept and the buffer value of Van Slyke was discussed.     

The determination of positive and negative co-operativity with allosteric enzymes and the interpretation of sigmoid curves and non-linear double reciprocal plots for the MWC and KNF models

(i) It is proved that only four independent constants can ever be obtained by extrapolation procedures applied to non-hyperbolic steady-state or binding data, (ii) Analysis of the algebraic graphs $\text{y}\text{x}$, $\text{(1/y)}\text{(1/x)}$, $\text{y}\text{(}\text{y}\text{x}\text{)}$ and ($\text{x}\text{y}\text{)/x}$ is shown to require a knowledge of the sign of six curve shape determinants. In each case, the sign is a necessary and sufficient condition for a specific curve shape feature, (iii) The precise graphical effect of positive and negative co-operativity then requires the definition of two reference curves, the osculating hyperbola at zero substrate concentration, OH(0), and the osculating hyperbola at infinite substrate concentration OH(∞). These are better first order approximations than the Hill equation, (iv) Rules for determining unambiguously the sign of initial, final and overall co-operativity coefficients by inspection of non-hyperbolic binding curves are then possible, (v) These rules require that saturation data for:

$\text{y=}\text{∑}\text{i=1}\text{n}\text{a}{}_{\mathrm{i}}\text{x}{}^{\mathrm{i}}\text{∑}\text{i=0}\text{n}\text{β}{}_{\mathrm{i}}\text{x}{}^{\mathrm{i}}$

be fitted by computer for low concentrations to the hyperbola:

$\text{OH}\text{(o)=}\text{(}\text{-a}{}_1{}^2\text{ψ}{}_{11}{}^{20}\text{)x}\text{[(}\text{-a}{}_1\text{β}{}_0\text{ψ}{}_{11}{}^{20}\text{)+x]}$

while regression of high substrate concentration data is to:

$\text{OH}\text{(∞)=}\text{(}\text{a}{}_{\mathrm{n}}\text{β}{}_{\mathrm{n}}\text{)x}\text{[(}\text{φ}{}_{\mathrm{n,n-1}}\text{a}{}_{\mathrm{n}}\text{β}{}_{\mathrm{n}}\text{)+x]}$

. Comparisons of the best fit pseudo-kinetic constants then gives the type of co-operativity present in an unambiguous way with no assumptions as to molecular mechanism, (vi) These rules are then applied to the MWC and KNF allosteric models of ligand binding and the constraints necessary for specific curve shape effects are given, (vii) The graphical expression of positive or negative final co-operativity depends only on events at high substrate concentration but overall and initial co-operativities produce specific geometric effects depending upon the difference between behaviour of saturation data at both extremes of concentration, (viii) This apparent anomaly is explained by a discussion of the relationships between the osculating hyperbolae, the theoretical parent hyperbola and the Hill plot asymptotes.     

Time lag in a model of a biochemical reaction sequence with end product inhibition

The model studied is that of Goodwin, in which all but one of the reactions obey linear kinetics, while the end-product inhibits the first reaction in a term of Michaelis-Menten form, with Hill coefficient ?:

$\text{z=}\text{∫}\text{?∞}\text{t}\text{x}{}_{\mathrm{n}}\text{(T)G(t?T)dt}$

The results obtained relate to time lag in the off diagonal terms in these equations. The time lag is taken in distributed form, for example replacing x_n in the first equation by

$\text{dx}{}_{\mathrm{t}}\text{dt}\text{=k}{}_1\text{x}{}_{\mathrm{t??}}\text{1?b}{}_1\text{x}{}_{\mathrm{t}}\text{, i=2, …n.}$

For any non-negative G, time lag in these terms can not destabilize the equilibrium point in the case ? = 1. For a particular class of functions G one can obtain some insight into the consequences of time lag by relating the model to that with a longer loop of reactions. Then known results can be used for general ? and n.     

Heterozygote frequencies in small subpopulations.

The mean fixation index within subpopulations (F_IS) has been defined as $\text{F}\text{̄}{}_{\mathrm{IS}}\text{= ∑w}{}_{\mathrm{i}}\text{F}{}_{\mathrm{ISi}}\text{or as}\text{F}\text{̂}{}_{\mathrm{IS}}\text{=}\text{∑w}{}_{\mathrm{i}}\text{p}{}_{\mathrm{i}}\text{q}{}_{\mathrm{i}}\text{F}{}_{\mathrm{ISi}}\text{∑w}{}_{\mathrm{i}}\text{p}{}_{\mathrm{i}}\text{q}{}_{\mathrm{i}}$. The latter definition is preferred because it can be obtained from the two other fixation indices, F_ST and F_IT and because it is unaffected by the mean gene frequency. The expected frequency of heterozygotes in small subpopulations of dioecious organisms will exceed Hardy-Weinberg expectations and this can be measured by $\text{F}\text{̂}{}_{\mathrm{IS}}$. In an isolated subpopulation of constant variance effective size $\text{N,}\text{F}\text{̂}{}_{\mathrm{IS}}$ rapidly tends to $\text{1 − 4N}{}^2\text{(N − 1 + [N}{}^2\text{+ 1]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}{}^2$. In the Island model of population structure, $\text{F}\text{̂}{}_{\mathrm{IS}}$ is approximately $\text{−(1 − m)}\text{N}\text{where}\text{m}$ is the immigration rate.When a sample is drawn from a natural population, the observed F_IS will depend upon the genetic structure of the population. The values of F_IS expected in three different types of population structure are discussed.     

Energetics of coupled Na+ and Cl− entry into epithelial cells of bullfrog small intestine

Na⁺, K⁺ and Cl^? concentrations ($\text{c}{}_{\mathrm{j}}{}^{\mathrm{<mtext>i</mtext>}}$) and activities ($\text{a}{}_{\mathrm{j}}{}^{\mathrm{<mtext>i</mtext>}}$), and mucosal membrane potentials ($\text{E}{}_{\mathrm{<mtext>m</mtext>}}$) were measured in epithelial cells of isolated bullfrog (Rana catesbeiana) small intestine. Segments of intestine were stripped of their external muscle layers, and bathed (at 25°C and pH 7.2) in oxygenated Ringer solutions containing 105 mM Na⁺ and Cl^? and 5.4 mM K⁺. Na⁺ and K⁺ concentrations were determined by atomic absorption spectrometry and Cl^? concentrations by conductometric titration following extraction of the dried tissue with 0.1 M HNO₃. ¹⁴C-labelled inulin was used to determine extracellular volume. $\text{E}{}_{\mathrm{<mtext>m</mtext>}}$ was measured with conventional open tip microelectrodes, $\text{a}{}_{\mathrm{<mtext>Cl</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ with solid-state Cl^?-selective silver microelectrodes and $\text{a}{}_{\mathrm{<mtext>Na</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ and $\text{a}{}_{\mathrm{<mtext>K</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ with Na⁺- and K⁺-selective liquid ion-exchanger microelectrodes. The average $\text{E}{}_{\mathrm{<mtext>m</mtext>}}$ recorded was ?34 mV. $\text{c}{}_{\mathrm{<mtext>Na</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$, $\text{c}{}_{\mathrm{<mtext>K</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ and $\text{c}{}_{\mathrm{<mtext>Cl</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ were 51, 105 and 52 mM. The corresponding values for $\text{a}{}_{\mathrm{<mtext>Na</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$, $\text{a}{}_{\mathrm{<mtext>K</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ and $\text{a}{}_{\mathrm{<mtext>Cl</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ were 18, 80 and 33 mM. These results suggest that a large fraction of the cytoplasmic Na⁺ is ‘bound’ or sequestered in an osmotically inactive form, that all, or virtually all the cytoplasmic K⁺ behaves as if in free solution, and that there is probably some binding of cytoplasmic Cl^?. $\text{a}{}_{\mathrm{<mtext>Cl</mtext>}}{}^{\mathrm{<mtext>i</mtext>}}$ significantly exceeds the level corresponding to electrochemical equilibrium across the mucosal and baso-lateral cell membranes. Earlier studies showed that coupled mucosal entry of Na⁺ and Cl^? is implicated in intracellular Cl^? accumulation in this tissue. This study permitted estimation of the steady-state transapical Na⁺ and Cl^? electrochemical potential differences (Δμ&#x0304;Na and Δμ&#x0304;Cl). Δμ&#x0304;Na (?7000 J · mol^?1; cell minus mucosal medium) was energetically more than sufficient to account for Δμ&#x0304;Cl (1000–2000 J · mol^?1).     

A unified approach to ion transport through membranes. I. Membrane-soluble ions.

Theoretical membrane potential transient produced by applying a current step to nerve cells has been derived based on the compartment neuron model and also on the equivalent cylinder model developed by W. Rall. It is expressed as a sum of exponential functions as

$\text{∑}\text{i=0}\text{n?1}\text{E}{}_{\mathrm{i}}\text{[1?}\text{exp}\text{(}\text{t}\text{τ}{}_{\mathrm{i}}\text{)]}$

where n is the number of compartments. The ratio of the amplitudes of the first and the second largest exponential functions, ($\text{E}{}_1\text{E}{}_0$), was found to be proportional to that of their respective time constants, ($\text{τ}{}_1\text{τ}{}_0$), in these neuron models. The constant of proportionality is given in a form that depends on the number of compartments as $\text{E}{}_1\text{E}{}_0\text{= (1 +}\text{cos}\text{π}\text{n}\text{)}\text{τ}{}_1\text{τ}{}_0$. This theoretical result is discussed in the light of recent experimental results in cat red nucleus neurons.     

A stable traveling-wave solution of a model of cellular control processes with positive feedback

Edelstein's model

$\text{?E}\text{?τ}\text{=F(M, E)}$

,

$\text{?M}\text{?τ}\text{=G(M, E)+D}\text{?}{}^2\text{M}\text{?s}{}^2$

,

$\text{M(s,0)=?(s)}$

,

$\text{E(s,0)=ψ(s)}$

, where τ ? 0 and ?∞<s<∞, $\text{F(M, E>) = (K}{}_1\text{+M}{}^{\mathrm{m}}\text{)}\text{(K}{}_2\text{+M}{}^{\mathrm{m}}\text{)?k}{}_1\text{E, G(M, E)}\text{= k}{}_1\text{E ? k}{}_2\text{M,}$ m ? 2, describes the behavior of two basic chemical species during the cellular differentiation in a linear ensemble of the same cell type. We prove the existence and uniqueness of a travelling-wavefront solution. We also demonstrate one kind of stability for this solution.     

Study on models of single populations: an expansion of the logistic and exponential equations

Using the adsorption theory of chemical kinetics, a new equation concerning the growth of single populations is presented:

$\text{d}\text{X}\text{d}\text{t}\text{=}\text{μ}{}_{\mathrm{c}}\text{X(1 ?)}\text{X}\text{X}{}_{\mathrm{m}}\text{1?}\text{X}\text{X}{}_{\mathrm{m}}{}^{\mathrm{\prime }}$

or in its integral form:

$\text{ln}\text{X}\text{X}{}_{\mathrm{o}}\text{?}\text{ln}\text{X}{}_{\mathrm{m}}\text{?X}\text{X}{}_{\mathrm{m}}\text{?X}{}_{\mathrm{o}}\text{+}\text{X}{}_{\mathrm{m}}\text{X}{}^{\mathrm{\prime }}{}_{\mathrm{m}}\text{X}{}_{\mathrm{m}}\text{?X}\text{X}{}_{\mathrm{m}}\text{?X}{}_{\mathrm{o}}\text{=μ}{}_{\mathrm{c}}\text{(t?t}{}_{\mathrm{o}}\text{)}$

This equation attempts to explain the relationship between population increment and limiting resources. It can be reduced to either the logistic or exponential equation under two extreme conditions. The new equation has three parameters, X_m, X′_m and μ_c, each of which has ecological significance. $\text{X}{}_{\mathrm{m}}\text{X′}{}_{\mathrm{m}}$ concerns the efficiency of nutrient utilization by an organism. Its value is between zero and one. With ratios approaching unity, the efficiency is high; lower ratios indicate that population increment is quickly restricted by limiting resources. μ_c, is a velocity parameter lying between μ_e, (exponential growth) and μ_L (logistic growth), and is dependent on the value of $\text{solX}{}_{\mathrm{m}}\text{X′}{}_{\mathrm{m}}$. From μ_c we can predict the time course of population incremental velocity ($\text{d}\text{X}\text{d}\text{t}$), and can observe that it is not symmetrical, unlike that derived from the logistic equation. At $\text{X}{}_{\mathrm{m}}\text{X′}{}_{\mathrm{m}}\text{= 1}$ the maximum velocity of the population increment predicted from the new equation is twice that of the logistic equation.Population growth in nature seems to support the new equation rather than the logistic equation, and it can be successfully fitted by means of a least square method.     

Reactions of the antitumor agent carminic acid and derivatives with DNA

The antitumor agent carminic acid 1a does not bind to DNA but nicks it slowly, more rapidly when reduced in situ, and still more rapidly when prereduced at the quinone moiety. The nicking process requires oxygen and is selectively inhibited by (i) superoxide dismutase, (ii) catalase, and (iii) free radical scavengers indicating the involvement of $\text{O}{}_2{}^{\mathrm{<mtext>?</mtext>}}\text{, H}{}_2\text{O}{}_2$, and OH^., respectively. The intermediacy of OH^. was supported by spin trapping with N-t-butyl-α-phenylnitrone and epr of the radical produced via the carminic acid semiquinone. The single strand scission of DNA by carminic acid requires two adjacent hydroquinone moieties in the chromophore since reduced methyl tetra-O-methylcarminate 1b is without effect although it binds weakly to DNA. Polarographic redox potentials for the reversible (2e, 2H⁺) reduction of 1a and 1b are ?0.736 ± 0.003 V and ?0.56 ± 0.010 V against SCE, respectively. The fact that daunorubicin and adriamycin produce more extensive DNA strand scission than carminic acid under comparable conditions of prereduction and on a molar basis is largely attributed to the assistance of intercalative binding afforded in the case of the anthracyclines.     

The covariance of relatives derived from a random mating population.

Attention is drawn to errors common in the derivation of forms for the genotypic covariance of noninbred relatives from a Hardy-Weinberg population of diploids. A synthesis of Fisher's least-squares method of partitioning the genotypic variance and Malécot's probability method of expressing kinship, yields a general form. For one locus, the form is $\text{(P}{}_{\mathrm{ss}}\text{+ P}{}_{\mathrm{sd}}\text{+ P}{}_{\mathrm{ds}}\text{+ P}{}_{\mathrm{dd}}\text{)}\text{1}\text{2}\text{σ}{}_{\mathrm{a}}{}^2\text{+ (P}{}_{\mathrm{ss}}\text{P}{}_{\mathrm{dd}}\text{+ P}{}_{\mathrm{sd}}\text{P}{}_{\mathrm{ds}}\text{) σa}{}_{\mathrm{d}}{}^2$, where σ_a² is the additive genetic variance, α_d² is the variance of dominance deviations, p_ij is the probability that parental gamete i is identical by descent to parental gamete j, i = s, d indexes the parents of one relative, and j = s, d indexes those of the other. The form provides a framework for obtaining the covariance of relatives from an equilibrium population with linkage.     

Nitro analogs of substrates for adenylosuccinate synthetase and adenylosuccinate lyase

The reactivities of the nitro analogs of the substrates of adenylosuccinate synthetase and adenylosuccinate lyase, the enzymes which catalyze the penultimate and last step, respectively, in the pathway for AMP biosynthesis have been examined. Alanine-3-nitronate, an aspartate analog, was a substrate for the synthetase from Azotobacter vinelandii, having a $\text{k}{}_{\mathrm{<mtext>cat</mtext>}}\text{K}{}_{\mathrm{m}}$ which was ~30% that for aspartate. The product of this reaction was N⁶-(l-1-carboxy-2-nitroethyl)-AMP. Of nine other substrate analogs tested, only cysteine sulfinate (having 5.5% of the activity of aspartate) was reactive. These results demonstrate the strict requirement of the synthetase for a negatively charged substituent, with a carboxylate-like geometry, at the β-carbon of the α-amino acid substrate. The lyase, purified to homogeneity from brewer's yeast by a new procedure, did not utilize N⁶-(l-1-carboxy-2-nitroethyl)-AMP as a substrate. However, the nitronate form of this analog was a good inhibitor of the lyase ($\text{K}{}_{\mathrm{m}}\text{K}{}_{\mathrm{i}}\text{= 28}$ when compared to adenylosuccinate), suggesting that it mimics a carbanionic intermediate in the reaction pathway. The avid binding of bromphenol blue by the lyase (_i = 0.95 μM) was used for active site titrations and for displacement of the enzyme, in the purification protocol, from blue Sepharose.     

Graphic method for determination of allosteric constants

The maximum slope of the plot, appearing in the paper of Watari & Isogai (1976), was derived algebraically as a function of allosteric constants c and α_mor β_m (= cα_m), and the relation between L, c, and α_mor β_m, was also obtained, where $\text{L =}\text{T}{}_{\mathrm{o}}\text{R}{}_{\mathrm{o}}\text{, c =}\text{K}{}_{\mathrm{R}}\text{K}{}_{\mathrm{T}}\text{, α}{}_{\mathrm{m}}\text{=}\text{F}{}_{\mathrm{m}}\text{K}{}_{\mathrm{R}}\text{, β}{}_{\mathrm{m}}\text{=}\text{F}{}_{\mathrm{m}}\text{K}{}_{\mathrm{T}}\text{, R}{}_{\mathrm{o}}\text{and}\text{T}{}_{\mathrm{o}}$ are concentrations of unligated R and T states respectively, K_Rand K_T are microscopic dissociation constants, and F_m is the ligand concentration at the maximum slope of the plot. When the maximum slope is increased by one, the value becomes Hill constant, n. Nomographs which enable easier estimation of allosteric constants, L and c, were constructed from the two given values, the maximum slope of the plot, n ? 1, and α_mor β_m, in the cases where the maximum number of ligands, N, was 2 and 4. In the nomograph, log c is plotted against log L²c^N keeping the value of the maximum slope of the plot and that of α_mor β_m constant. These nomographs show that the representation is symmetrical in the cases of L²c^N > 1 and L²c^N < 1.     

Bovine fibrinogens: Reversible polymer formation

Reversible flbrinogen polymer formation was examined at pH 6.6 and Γ/2 0.3. The equilibrium fraction of fibrinogen present as polymer, (P_mf)_e, was determined by gel filtration for fibrinogen concentrations, F_O, from 48 to 166 μm. Using F_O in molarity, the experimental relation is ln [F_O(P_mf)_e] = 3.53 ln[F_O(1 ? (P_mf)_e)] + 23.73. This relation and attendant confidence limits are examined assuming, during filtration, that the original polymer population is either stable or selected polymer species dissociate to monomer. The possibility that all polymers are open is excluded since the calculated microscopic association constant would then increase with F_O. Acceptable models are based on the assumptions that polymers are open, with association constant K_a, until restricted by closure, with association constant K_r, at an integral degree of polymerization, n. Values are selected on the basis that interaction parameters are independent of F_O and that the required molar decrease in free energy is a minimum. Assuming polymer stability, the experimental relation at 273 °K gives $\text{n = 4,}\text{K}{}_{\mathrm{r}}\text{K}{}_{\mathrm{a}}\text{= 1.2 m,}\text{and}\text{K}{}_{\mathrm{a}}$ = 736 m^?1. Temperature dependence gives $\text{ΔH= ?16.9 kcal/mol}\text{and}\text{ΔS}{}^{\mathrm{O}}{}_{\mathrm{a}}$ = ?48.8 e.u. $\text{K}{}_{\mathrm{r}}\text{K}{}_{\mathrm{a}}$ indicates a relation between changes in entropy. The probability is >0.90 that $\text{K}{}_{\mathrm{r}}\text{K}{}_{\mathrm{a}}\text{? 56 m}$, which indicates a greater loss of degrees of freedom on closure than on association. Conclusions are not altered by the assumption that only the closed polymer species is stable. As ionic strength is decreased at pH 6.6, K_a increases. The clotting time of an otherwise constant system decreases as system P_mf is increased.     

Kinetic and thermodynamic properties of membrane-bound cytochromes of aerobically and photosynthetically grown Rhodopseudomonas spheroides

A green mutant of Rhodopseudomonas spheroides was isolated in which spectroscopic measurements of the α-band region of cytochromes could be made. It was grown either aerobically or photosynthetically, and the membrane fractions prepared from cells of each type. Anaerobic potentiometric titration at 560 nm minus 542 nm showed the same three redox components, tentatively identified as b-type cytochromes, in membrane fractions from either type of cell. The mid-point potentials were approximately +185, +41 and ?104 mV. In membranes from photosynthetically grown cells the major cytochrome form absorbing at 560 nm had a mid-point potential of +42 mV; in aerobically grown cells the major form had a potential of +185 mV. In both types of cell only one c-type cytochrome was found, with a mid-point potential of +295 mV. An a-type cytochrome was present only in aerobically-grown cells.Substrate-reduced particles from these cells were mixed with air-saturated buffer in a stopped-flow spectrophotometer and the kinetics of oxidation of b- and c-type cytochromes were measured. The same two b-type components, reacting with pseudo first order kinetics, were detected in particles from both aerobically and photosynthetically grown cells ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ for oxidation 1.3 s and 0.13 s). The c-type cytochrome of particles from aerobically grown cells was oxidised with $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of 0.97 s; the c-type cytochrome of photosynthetic cells was oxidised faster, with $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of 0.27 s.These observations have implications on the adaptive formation of electron transport systems that are discussed.     

Restoration of pool function type behavior to succinate dehydrogenase having latent reconstitutive activity in ubiquinol-cytochrome c reductase complex

Mitochondrial ubiquinol-cytochrome $\text{c}$ reductase complex contains small amounts of succinate dehydrogenase. Estimates from electrophoresis indicate there is one dehydrogenase per eight complexes. This dehydrogenase transfers electrons to the $\text{b}$-$\text{c}{}_1$ complex poorly, as judged by low succinate-ubiquinone and succinate-cytochrome $\text{c}$ reductase activities. Electron transfer to the $\text{b}$-$\text{c}{}_1$ complex is restored by reconstitution of the complex with phospholipid. This phospholipid dependent restoration of electron transfer indicates that either reconstitutive activity of the dehydrogenase is preserved under conditions where electron transfer is absent, or that addition of phospholipid allows one dehydrogenase to transfer electrons to multiple $\text{b}$-$\text{c}{}_1$ complexes.     

Evidence for a protonmotive Q cycle mechanism of electron transfer through the cytochrome b-c1 complex.

A protein named oxidation factor can be reversibly removed from succinate-cytochrome $\text{c}$ reductase complex and shown to be required for electron transfer between succinate and cytochrome $\text{c}$. This protein is required for reduction of cytochrome $\text{c}{}_1$ and, in the presence of antimycin, for reduction of both cytochromes $\text{b}$ and $\text{c}{}_1$. These results are consistent with a protonmotive Q cycle mechanism in which the oxidation factor catalyzes electron transfer from reduced quinone to cytochrome $\text{c}{}_1$ and thus liberates from reduced quinone one of two protons required for energy conservation during electron transfer through the cytochrome $\text{b}\text{-}\text{c}{}_1$ complex.     

Electron diffraction study on single crystals of l-type and dl-type lecithins

An electron diffraction study was carried out on thin single micro-crystals of l-type and dl-type dipalmitoyl lecithins grown in xylene suspensions and fine net patterns were obtained and the mechanism of the thermotropic phase transitions of them was clarified.From the apparent structure of diffraction patterns in low temperature, it is confirmed that the two dimensional lattices have p mm symmetry in l-type and in dl-type lecithins. Lattice parameters from the [001] projection are $\text{d}{}_{100}\text{= 9.9}\text{A}\text{?}$ and $\text{d}{}_{010}\text{= 8.8}\text{A}\text{?}$ in l-type, and $\text{d}{}_{100}\text{= 17.2}\text{A}\text{?}$ and $\text{d}{}_{010}\text{= 8.9}\text{A}\text{?}$ in dl-type.With anisotropic variation of dimensions along a and b axes, i.e. contraction for a and expansion for b, induced by temperature rise by electron irradiation during the observation, these diffraction patterns of the lattices of l-type and dl-type were transformed into those characterized by the six diffraction spots having nearly the same spacings. Four of them are observed on slightly outer and two are slightly inner positions as compared with their mean spacings of about (4.1 Å)^?1 in l-type and about (4.2 Å)^?1 in dl-type. The changes in the patterns observed indicate that at low temperatures the hydrocarbon chains are nearly perpendicular to the layer in dl-type lipid, and tilted with a more complicated packing in l-type ones. The dimension along a in dl-type is twice as large as that in l-type.