# X-ray Crystallography: Data Processing Summary Quiz

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Quizzes Created: 1 | Total Attempts: 340
Questions: 10 | Attempts: 340

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• 1.

### What must we do to our crystal to collect the various reflections we need to analyse our protein?

• A.

Rotate it

• B.

Nothing

• C.

Use computer software to predict these other reflections

• D.

Look at the signal:noise ratio to separate these other reflections from background noise

A. Rotate it
Explanation
To collect the various reflections needed to analyze the protein, we must rotate the crystal. This is because rotating the crystal allows different angles of the crystal lattice to be exposed to the X-ray beam, resulting in different reflections. By rotating the crystal, we can obtain a wider range of reflections, which helps in the analysis of the protein structure.

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• 2.

### Mosflm is one of the many statistics we use analyse the quality of our data.

• A.

True

• B.

False

B. False
Explanation
Mosflm is not a statistic but rather a software program used for processing diffraction data from macromolecular crystals. It is not used to analyze the quality of data but rather to determine the orientation and intensity of the diffracted X-rays. Therefore, the statement is false.

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• 3.

### The number of unique reflections is the total number of reflections measured during an experiment.

• A.

True

• B.

False

B. False
Explanation
The statement is false because the number of unique reflections is not the total number of reflections measured during an experiment. Unique reflections refer to the distinct or different reflections that are observed, which may be fewer in number than the total reflections measured. This is because some reflections may be repeated or overlapping, leading to a smaller count of unique reflections.

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• 4.

### What must you do before analysing your data statistically?

• A.

Decide on a likely lattice type and unit cell size

• B.

Calculate amplitudes of diffracted waves

• C.

Identify and get rid of any noise in the diffraction data

• D.

Determine the asymmetric unit and the unit cell size

A. Decide on a likely lattice type and unit cell size
B. Calculate amplitudes of diffracted waves
Explanation
Before analyzing the data statistically, it is important to decide on a likely lattice type and unit cell size. This is because the lattice type and unit cell size determine the symmetry and arrangement of the crystal structure, which is crucial for further analysis. Additionally, calculating the amplitudes of diffracted waves is necessary as it provides information about the intensity of the diffraction pattern, which is essential for statistical analysis. These steps help in accurately interpreting and understanding the data before performing statistical analysis.

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• 5.

### Why do we measure the intensity of our diffraction spots?

• A.

To give us a list of reflection intensities we can compare

• B.

To give us statistical information

• C.

To help determine the lattice type and space group

• D.

To give an indication of the quality of our data

A. To give us a list of reflection intensities we can compare
B. To give us statistical information
Explanation
We measure the intensity of our diffraction spots to give us a list of reflection intensities that we can compare. This allows us to analyze the diffraction pattern and determine the relative strengths of different reflections. By comparing the intensities, we can gain statistical information about the crystal structure, such as the arrangement of atoms in the lattice. Additionally, the intensity measurements can help us determine the lattice type and space group, providing further information about the crystal's symmetry and arrangement of atoms. Furthermore, the intensity measurements can also give us an indication of the quality of our data, helping us assess the accuracy and reliability of our experimental results.

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• 6.

### Deciding on a unit cell size is part of the first step of processing your data.

• A.

True

• B.

False

A. True
Explanation
Deciding on a unit cell size is indeed part of the first step of processing data. In crystallography, a unit cell is the smallest repeating unit of a crystal lattice. Determining the appropriate unit cell size is crucial for accurately analyzing and interpreting the data obtained from crystallographic experiments. By defining the unit cell dimensions, scientists can calculate important parameters such as lattice constants, symmetry elements, and atomic positions. Therefore, it is correct to say that deciding on a unit cell size is an essential step in the data processing stage.

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• 7.

### Which of the following is an indication of data quality?

• A.

Whether spots are where you expect them to be

• B.

R-Factor

• C.

The list of spot intensities

• D.

R-Free

A. Whether spots are where you expect them to be
Explanation
An indication of data quality can be determined by whether the spots are where you expect them to be. This suggests that the data is accurate and reliable, as the expected spots align with the actual spots observed. If the spots are not where they are expected to be, it may indicate errors or inconsistencies in the data, which can affect the overall quality and reliability of the information.

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• 8.

### Why do we get two values for each statistic?

• A.

One for all the data, and one for those at the edge of the detector

• B.

One for inner reflections, and one for outer reflections

• C.

One for high and low resolution data

A. One for all the data, and one for those at the edge of the detector
Explanation
The reason we get two values for each statistic is because we want to analyze the data from different perspectives. One value represents the overall data, giving us a general understanding of the statistic. The other value specifically focuses on the data at the edge of the detector, which might have different characteristics or be subject to different conditions. By comparing these two values, we can gain insights into the variations and potential biases in the data, helping us to make more accurate interpretations and conclusions.

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• 9.

### Some statistical information can be gathered, before the processing of diffraction data.

• A.

True

• B.

False

B. False
Explanation
The statement suggests that statistical information can be collected before processing diffraction data. However, this is incorrect. Statistical information is typically gathered after the processing of diffraction data, as it involves analyzing the data and drawing conclusions based on the results obtained. Therefore, the correct answer is False.

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