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A spirochaete is a member of a distinctive group of elongated, flexible bacteria with flagella housed in the periplasm, between the inner cellular body and outer cell membrane. These internal flagella contribute to characteristic bending or wave-like movement. A spiral-looking outline alone does not identify a spirochaete.

In Borrelia burgdorferi, disrupting the gene for a major flagellar protein produced nonmotile, rod-shaped cells in place of the normal flat-wave form. Thus the internal flagellar apparatus contributes both to motion and to body shape.^[ref] Some spirochaetes cause disease, including Lyme disease, but the group is defined by evolutionary and cellular relationships, not by one clinical outcome.

The dynamic RNA–protein machinery carrying out spliceosomal intron removal. Regulatory interference can occur during early assembly or later catalytic transitions.

A protein kinase whose substrates include regulatory proteins involved in cell migration and local biological translation.

S. Rea is the first author of a 2000 study identifying SUV39H1 and its mouse counterpart as histone methyltransferases with a specific target: lysine 9 near the beginning of histone H3. In experiments outside living biological cells, these enzymes transferred methyl groups to that position. Mapping the catalytic activity implicated the SET domain together with neighboring regions rich in cysteine.^[ref]

The specificity is the important idea: a histone modification has an address within a protein, rather than simply changing the bulk composition of chromatin. The study also found that modification of lysine 9 interfered with phosphorylation of neighboring serine 10, illustrating how nearby chemical changes can interact. Experiments that altered the enzymes' activity in biological cells also changed histone H3 phosphorylation and produced abnormal divisions. These observations helped connect a defined catalytic reaction with the regulation of chromatin; they did not imply that every modified histone has the same effect in every biological context.^[ref]

Researcher in localized translation. Hüttelmaier and collaborators investigated Src-dependent phosphorylation of ZBP1 in control of beta-actin translation, connecting a signaling event with where a protein is synthesized.^[ref]

Steven D. Marlin is a researcher whose work helped identify a molecular pair involved in cell adhesion. In a 1987 study with T. A. Springer, Steven D. Marlin tested whether purified ICAM-1 could bind biological cells carrying LFA-1.^[ref]

The investigators incorporated purified ICAM-1 into artificial supported lipid bilayers. Cells carrying LFA-1 bound, while the negative comparison cells did not. Antibodies against either partner inhibited the interaction when applied to the corresponding surface.^[ref]

Reconstitution narrowed the explanation. Adhesion between two intact biological cells might depend on many surface components; supplying one purified candidate in an artificial membrane reduced that complexity. Blocking each side independently then tested whether both identified proteins contributed to the measured attachment.

Researcher in chromatin biology and bioinformatics. With Jorja G. Henikoff, Henikoff developed amino acid substitution matrices from conserved protein blocks; these provide empirically grounded scores for comparing protein sequences.^[ref]

Stewart Shuman is a biochemist who investigates how enzymes modify and repair nucleic acids. His laboratory combines biochemistry, structural biology and genetics to connect a particular chemical reaction with the protein machinery that performs it.^[ref]

With Anupam K. Chakravarty, Shuman tested competing reaction mechanisms for the RNA ligase RtcB. The question concerned the chemistry of the broken RNA ends: did a cyclic phosphate join directly to an opposing hydroxyl end, or did opening and activation precede sealing? Their 2012 experiments supported a GTP-dependent pathway involving hydrolysis, activated reaction intermediates and formation of a new phosphodiester bond.^[ref]

The logical force of such an experiment can be seen without assuming that a successful final reaction reveals every step. Suppose mechanisms A and B both predict a joined RNA molecule, but A requires GTP even when the starting end already contains a cyclic phosphate, whereas B predicts that this substrate bypasses the GTP requirement. Comparing otherwise equivalent reactions with and without GTP distinguishes those predictions. Detecting an intermediate also requires attention to chemical kinetics: a species appearing only after product accumulation cannot explain an earlier obligatory step. These are general reasons to combine selective changes in starting chemistry with time-resolved measurements, rather than identifying a reaction mechanism solely from the final product.

Streptavidin is a biotin-binding protein widely used to capture or label biotinylated material. Its tetrameric assembly provides multiple binding sites and can therefore crosslink tagged components. Strong binding makes the pair useful for retention during measurements, but multivalency and steric accessibility affect the resulting geometry. Capture of a biotinylated molecule demonstrates access to the tag, not necessarily preservation of every native molecular interaction. ^[ref]

A stress-associated RNA–protein assembly whose formation and composition depend on context. RNA enrichment does not establish obligatory translational silence.^[ref]

A prior stimulus changes the response to a subsequent challenge. Persistence may involve metabolites, proteins, regulatory feedback or chromatin; priming alone does not establish epigenetic inheritance.

A stress response is a coordinated change in cellular activity caused by conditions that threaten normal function, such as excessive temperature, nutrient shortage or damaged proteins. It can alter gene expression, protein degradation and metabolism. For example, increased production of molecular chaperones helps handle unfolded proteins. The response is protective only within limits: prolonged or severe stress can cause cell death. Measuring response markers therefore establishes detection of stress, not necessarily successful recovery. ^[ref]

subcellular localization is the distribution of a component among cellular regions or compartments. Changing localization can change a protein's partners even when its total abundance is constant.

Sulfur-35 is a radioactive isotope of sulfur with 16 protons and 19 neutrons. It undergoes beta-minus decay to stable chlorine-35. The cited evaluation gives a half-life of $87.25(15)\mathrm{d}$, much longer than the roughly 14-day half-life of phosphorus-32.^[ref]

The 1952 Hershey-Chase experiment used sulfur-35 to follow the sulfur-containing protein component of Bacteriophage T2. Agitation released about 75 percent of the phage sulfur label, compared with about 15 percent of the phosphorus label, while the infected cells could still yield progeny. The complementary labels helped separate the fates of external protein and entering DNA.^[ref] A label identifies the material carrying it under the specified labelling scheme; detection alone does not establish the function of every component.

Using the quoted half-life, a closed sample observed 14 days later retains $2^{-14/87.25}\approx 0.895$ of its starting radioactivity. That is about 90 percent, rather than one half. Comparing sulfur-35 and phosphorus-32 signals over days therefore requires isotope-specific decay accounting. Detector efficiency and recovery of labelled material also belong to the measurement model; equal raw counts do not automatically mean equal numbers of labelled atoms.

A repeated peptide-epitope system detectable by fluorescent binders. Placing tags on nascent chains can make a biological translation site visible separately from completed proteins.

SUV39H1 is a human histone methyltransferase that modifies lysine 9 in the amino-terminal region of histone H3. Its catalytic machinery includes a SET domain and adjoining cysteine-rich regions. The corresponding gene encodes an enzyme acting on a protein component of chromatin.^[ref]

The original biochemical work established site specificity using histone H3 substrates and mapped the catalytic requirement to regions of SUV39H1. It also found that lysine 9 methylation interfered with phosphorylation of neighbouring serine 10. This gives an illuminating example of interacting histone modifications: changing one residue can affect a modification at the next residue, so the histone tail is a chemically coupled substrate.^[ref]

For an enzyme assay, the informative measurement is formation of the specified methylated histone product. Simply detecting SUV39H1 expression establishes the presence of its protein, while activity additionally depends on the reaction conditions and available substrate.

Coauthor of experiments identifying a nucleoplasmin region that specifies migration into the cell nucleus. The study connected a defined part of a protein with selective nuclear targeting; the documented initials are retained without an unverified full-name expansion.^[ref]

A synaptic vesicle is a small membrane-bounded compartment in a presynaptic terminal that stores neurotransmitter for release. Fusion with the cell membrane exposes its contents to the synaptic cleft; the packet supplied by one synaptic vesicle is a quantum of release. Quantal neurotransmitter release refers to these discrete packets, rather than the release of one molecule at a time. The postsynaptic response to a packet can vary with its contents, receptors and recording conditions. See Purves and colleagues: vesicles as the source of transmitter quanta.

The useful cycle is filling, preparation for fusion, calcium-triggered exocytosis, and recovery of membrane and proteins through endocytosis for reuse. Different recovery routes occur; recycling need not preserve a particular synaptic vesicle as an identifiable container throughout. Limited availability of prepared synaptic vesicles can reduce release during repeated stimulation, while changes in synaptic release probability can also change successive responses. See Basic Neurochemistry: secretion machinery and vesicle reuse and 3.1 Synapses.

For an illustrative calculation, assume four release sites, each with one prepared synaptic vesicle, each releasing with synaptic release probability $p=0.25$ during one presynaptic action potential. Assume independent Bernoulli trials and at most one release per site. The released packet count $K$ has a binomial distribution:The probability of no release is $\mathbb{P}(K=0)=0.75^4=0.31640625$; at least one release has probability $0.68359375$. An expected value of one packet does not mean that every action potential releases one packet. If each packet contributes a stipulated $0.5\mathrm{nS}$ conductance increment and increments add, the expected value of that increment is $0.5\mathrm{nS}$, with zero increment on about $31.6\%$ of trials. These assumptions are a teaching model: shared calcium fluctuations, unequal sites, depletion and nonlinear receptor responses can invalidate them.

Synaptobrevin is a membrane-anchored SNARE protein associated with secretory vesicles, including synaptic vesicles. Its cytosolic helix joins complementary helices from syntaxin and SNAP-25 to form a SNARE complex. When the partners initially occupy opposing lipid bilayers, their assembly helps bring those lipid bilayers close enough for membrane fusion. The protein helps couple the membranes mechanically; it is not a pore through which the neurotransmitter simply leaks. ^[ref]

Reconstituting synaptobrevin and its complementary SNARE proteins into separate liposomes made fusion measurable outside a cell. The ability to accumulate docked intermediates at low temperature and trigger fusion on warming also distinguished membrane docking from the subsequent merger. Living synapses add regulation that this minimal assay does not reproduce. ^[ref]

The synaptonemal complex is an organized protein scaffold assembled between aligned homologous chromosomes during Prophase I of meiosis. Two lateral elements run along the homologues, and transverse components connect them through a central region. Its zipper-like appearance makes chromosome synapsis visible, but the structure itself is not a completed exchange of DNA.

Yeast mutants lacking functional Zip1 helped separate these events. Homologues could pair, yet normal synaptonemal complex assembly failed and meiotic progression was disrupted. The comparison distinguishes initial recognition and alignment from construction of the full scaffold.^[ref] This is why a microscopy image showing nearby chromosomes should not automatically be interpreted as evidence for a completed crossing over.